# Comparison of email clients

The following tables compare general and technical features of notable non-web-based email client programs.

## General

Basic general information about the clients: creator/company, O/S, license, and interface.
| Client | Author/Developer | Operating system | Software license | User Interface |
| Alpine | University of Washington | Cross-platform | Apache-2.0 | TUI |
| Apple Mail | Apple | macOS, iOS, watchOS | Proprietary | GUI (Cocoa) |
| Balsa | Stuart Parmenter | Linux | GPL-2.0-or-later | GUI (GTK3) |
| Becky! Internet Mail | Rimarts | Windows | Proprietary | GUI |
| BlitzMail | Dartmouth College | | BSD licenses | GUI |
| Canary Mail | Cartasec Pte. Ltd. | Cross-platform | Proprietary | GUI |
| Citadel | citadel.org | Unix-like | GPL-3.0-only | Webmail |
| Claws Mail | the Claws Mail team | Cross-platform | GPL-3.0-or-later | GUI (GTK2) |
| Courier (formerly Calypso) | Micro Computer Systems, Inc., continued by Rose City Software | Windows | Proprietary | GUI |
| Elm | Dave Taylor, Sydney Weinstein, Bill Pemberton, Michael Elkins, Kari Hurtta | Unix-like | BSD-like | TUI |
| eM Client | eM Client Inc. | Windows, macOS, Android, iOS | Proprietary | GUI |
| EmailTray | Internet Promotion Agency S.A. | Windows, Android | Proprietary | GUI |
| Eudora OSE | Qualcomm | Windows, macOS | Open source | GUI |
| Evolution | The GNOME Project | Unix-like | LGPL-2.1-only or LGPL-3.0-only | GUI (GTK) |
| FirstClass | Open Text | | Proprietary | GUI |
| Forté Agent | Mark Sidell | Windows | Proprietary | GUI |
| Geary | The GNOME Project (formerly Yorba Foundation) | Unix-like | LGPL-2.1-or-later | GUI (GTK) |
| GNUMail | Ludovic Marcotte and others | Unix-like, macOS | GPL-2.0-or-later | GUI |
| Gnus | Gnus team | Cross-platform | GPL-3.0-or-later | TUI and GUI |
| GroupWise | Micro Focus (formerly Novell) | Cross-platform | Proprietary | GUI |
| Hiri | Hiri | Cross-platform | Proprietary | GUI |
| i.Scribe, InScribe | Memecode | Windows, macOS, Linux | GPL-3.0-only | GUI |
| HCL Notes (formerly IBM Notes and IBM Lotus Notes) | HCL Technologies (formerly IBM and Lotus Software), HCL Technologies | Windows, macOS, Linux | Proprietary | GUI (Notes), Web (Verse, iNotes) and Mobile (Traveler) |
| IMP | Horde LLC | Cross-platform | GPL-2.0-only | Webmail |
| K-9 Mail | K-9 Dog Walkers: cketti, et al. | Android | Apache-2.0 | GUI |
| KMail | KDE | Cross-platform | GNU General Public License | GUI (Qt) |
| Mail (Windows) | Microsoft | Windows | Proprietary | GUI |
| Mailbird | Mailbird | Windows | Proprietary | GUI |
| Mailpile | Mailpile | Windows, macOS, Linux | AGPL-3.0-or-later | Webmail |
| mailx | ? | Unix-like | BSD Licenses | TUI |
| Microsoft Entourage | Microsoft | macOS | Proprietary | GUI |
| Microsoft Outlook | Microsoft | Windows, macOS | Proprietary | GUI |
| Mozilla Mail & Newsgroups | Mozilla Foundation | | Mozilla Public License | GUI (XUL) |
| Mozilla Thunderbird | Mozilla Foundation | Cross-platform | MPL-2.0 | GUI (XUL) |
| Mulberry | Cyrus Daboo (formerly Cyrusoft International, Inc./ISAMET) | Cross-platform | Apache-2.0 | GUI |
| Mutt | Michael Elkins | Cross-platform | GPL-2.0-or-later | TUI (ncurses) |
| Netscape Messenger | Netscape Communications | | ? | GUI |
| Netscape Messenger 9 | Netscape Communications | | Mozilla Public License | GUI |
| Nylas Mail | Nylas | Windows, macOS, Linux | MIT | GUI |
| nmh / MH | RAND Corporation | Unix-like | BSD Licenses | CLI |
| Opera Mail | Opera Software | Cross-platform | Proprietary | GUI |
| Outlook Express | Microsoft | Windows | Proprietary | GUI |
| Pegasus Mail | David Harris | Windows | Proprietary | GUI |
| Pine | University of Washington | Cross-platform | Freeware | TUI |
| Pocomail | Poco Systems | Windows | Proprietary | GUI |
| RoundCube | The RoundCube Team | Cross-platform | GPL-3.0-or-later | Webmail |
| Samsung Email | Samsung Electronics | Samsung, Android 8+ | Proprietary | GUI |
| SeaMonkey Mail & Newsgroups | SeaMonkey Council | Cross-platform | MPL-2.0 | GUI (XUL) |
| Spark | Readdle | macOS | Proprietary | GUI |
| SquirrelMail | The SquirrelMail Project Team | Cross-platform | GPL-2.0-or-later | Webmail |
| Superhuman | Rahul Vohra | Cross-platform | Proprietary | Webmail |
| Sylpheed | Hiroyuki Yamamoto | Cross-platform | Sylpheed: GPL-2.0-or-later LibSylph: LGPL-2.1-or-later | GUI (GTK2) |
| The Bat! | RitLabs | Windows | Proprietary | GUI |
| Trojitá | KDE | Cross-platform | GPL-2.0-only or GPL-3.0-only | GUI (Qt) |
| Turnpike | Thus PLC (Demon Internet) | Windows | Proprietary | GUI |
| Vivaldi | Vivaldi Technologies AS | Cross-platform | Proprietary | GUI (Chrome) |
| Windows Live Mail | Microsoft | Windows | Proprietary | GUI |
| Windows Mail (Vista) | Microsoft | Windows | Proprietary | GUI |
| YAM | YAM Open Source Team and contributing authors | AmigaOS | GPL-2.0-or-later | GUI |
| Zimbra Desktop | Zimbra | Cross-platform | Mozilla Public License for server and ZPL for client | GUI |
| Client | Author/Developer | Operating system | Software license | User interface |
* ↑ Or LicenseRef-KDE-Accepted-GPL: "Any later version accepted by the membership of KDE e.V. (or its successor approved by the membership of KDE e.V.), which shall act as a proxy defined in Section 14 of version 3 of the license."

## Release history

A brief digest of the release histories.
| Client | First public Date | First public Version | First stable Date | First stable Version | Latest stable release |
| Alpine | 2006-11 | 0.8 | 2007 December | 1.00 | 2.26 2 June 2022 |
| Apple Mail | 2001-03-24 | ? | ? | ? | ( ) |
| Becky! Internet Mail | 1996 | 1 | ? | ? | 2.81.06 28 February 2024 |
| Canary Mail | 2017-06-15 | 1.0 | 2017-06-15 | 1.0 | 4.01 (5th June, 2023) |
| Citadel | 1987 | ? | 1988 | 1.00 | 997 29 January 2024 |
| Claws Mail | 2001-05 | 0.4.67 | 2005-01 | 1.0.0 | 4.3.1 24 February 2025 |
| Courier | 2004-06 | 3.5 | discontinued | discontinued | 3.5 (June 2004) |
| Elm | 1986 | ? | 1987-03 | 2 | 2.5.8 18 August 2005 |
| eM Client | 2007-11 | 1.0 | 2007-11 | 1.0 | 10.1.5131.0 (February 13, 2025; 27 days ago (2025-02-13)) |
| EmailTray | 2010-10 | 2.0 | 2011-03 | 3.11 | 4.0 (July 2, 2012; 12 years ago (2012-07-02)) |
| Eudora | 1988 | ? | 1988 | ? | 7.1 (Windows), 6.2.4 (Mac OS) (October 11, 2006; 18 years ago (2006-10-11)) |
| Evolution | 2000-05-11 | 0.0 | 2001-12-03 | 1.0 | 3.54.3 3 January 2025 |
| Forté Agent | ? | ? | ? | ? | 8 (October 20, 2014; 10 years ago (2014-10-20)) |
| Geary | 2012 | 0.1 | 2012 | 0.1 | 46.0 20 May 2024 |
| Gnus | 1987 | ? | 1988-02-01 | 2.0 | 2015-04-06 |
| GroupWise | ? | ? | 1986 | 1.0 | 18.4 14 March 2022 |
| Hiri | 2014-02 | 0.4 | 2016-06 | 1.0 | 1.0.11 (June 10, 2017; 7 years ago (2017-06-10)) |
| i.Scribe / InScribe | 1999 | 1.00 | ? | ? | 2.3.18 (March 30, 2021; 3 years ago (2021-03-30)) |
| HCL Notes (formerly IBM Lotus Notes) | 1989 | 1.0 | 1989 | 1.0 | 14.0.0 7 December 2023 |
| IMP | ? | ? | 1998 | 1.0 | 6.2.27 27 August 2020 |
| K-9 Mail | ? | ? | ? | ? | 8.2 10 December 2024 |
| KMail | 1998-10 | Alpha | 1999-02 | 1.0.17 | 24.11.90 27 November 2024 |
| Mailbird | 2013-04-01 | Public Beta | ? | ? | 2.9.29 (April 22, 2021; 3 years ago (2021-04-22)) |
| Mailpile | 2011-11 | | | | 1.0.0rc6 (September 4, 2019; 5 years ago (2019-09-04)) |
| Microsoft Entourage | ? | ? | ? | ? | 2008 (12.3.6) (March 12, 2013; 12 years ago (2013-03-12)) |
| Microsoft Office Outlook | 1997 | 97 | 1997 | 97 | Microsoft 365 & Retail (Windows)2502 (Build 18526.20144) / 5 March 2025; 7 days ago (2025-03-05)Microsoft 365 (Mac)16.94.2 (Build 25022327) / 25 February 2025; 15 days ago (2025-02-25)Office 2021 (LTSC)2108 (Build 14332.20857) / 11 February 2025; 29 days ago (2025-02-11)Office 2019 (LTSC)1808 (Build 10416.20058) / 11 February 2025; 29 days ago (2025-02-11) |
| Mozilla Thunderbird | 2003-07-28 | 0.1 | 2004-12-07 | 1.0 | 136.0 4 March 2025 |
| Mulberry | 1996-09-20 | 1.0 | 1996-09-20 | 1.0 | 4.0.8 (February 21, 2007; 18 years ago (2007-02-21)) |
| Mutt | 1995 | ? | ? | ? | 2.2.14 20 February 2025 |
| Netscape Messenger | ? | ? | ? | ? | 7.2 (August 17, 2007; 17 years ago (2007-08-17)) |
| Netscape Messenger 9 | 2007-11-15 | 9.0a1 | discontinued | discontinued | 2007-11-15 |
| nmh / MH | 1979 | ? | ? | ? | 1.5 (June 11, 2012; 12 years ago (2012-06-11)) |
| Opera Mail | 1996-09 | 2.1b1 | 1996-12 | 2.1 | 1.0.1044 (February 16, 2016; 9 years ago (2016-02-16)) |
| Outlook Express | 1996 | 3.0 | ? | ? | |
| Pegasus Mail | 1990 | ? | 1990 | ? | 4.80 14 February 2022 |
| Pine | 1992-01-15 | 2.00 | 1992-01-15 | 2.00 | 4.64 28 September 2005 |
| Pocomail | 1999 | ? | ? | ? | 4.8 build 4400 (April 6, 2009; 15 years ago (2009-04-06)) |
| RoundCube | 2006 | 0.1-rc1 | 2014-04-07 | 1.0.0 | 1.6.10 8 February 2025 |
| SeaMonkey Mail & Newsgroups | 2005-09-15 | 1.0a | 2006-01-30 | 1.0 | 2.53.20 7 January 2025 |
| SquirrelMail | 1999-12 | 0.1 | 2001-01 | 1.0 | |
| Sylpheed | 2000-01 | 0.1.0 | 2004-12 | 1.0.0 | 3.7 31 January 2018 |
| The Bat! | 1997-03 | 1.0 Beta | 1998-03 | 1.00 Build 1310 | |
| Trojitá | 2009-08 | 0.1 | 2012-12 | 0.3.90 | |
| Turnpike | 1996 (circa) | 1.0 | 1996 (circa) | 1.0 | 6.06 (May 23, 2006; 18 years ago (2006-05-23)) |
| Vivaldi | 2015-11-03 | Beta 1 | 2022-06-09 | 1.0 | |
| Windows Live Mail | 2007-11-06 | 12 | 2007-11-06 | 12 | 2012 (v16.4.3528.0331) (November 4, 2014; 10 years ago (2014-11-04)) |
| Windows Mail | ? | ? | ? | ? | 2007-01-01 |
| YAM | 1995 | 1.0 | 1995 | 1.0 | 2.9p1 27 April 2016 |
| Zimbra | 2005-11 | Beta | 2006-03 | 3.5 | 8.6.0 (December 15, 2014; 10 years ago (2014-12-15)) |

## Operating system support

The operating systems on which the clients can run natively (without emulation).
| Client | Microsoft Windows | macOS | Linux | BSD | Unix | DOS | Other |
| Alpine | Yes | Yes | Yes | Yes | Yes | No | No |
| Apple Mail | No | Included | No | No | No | No | No |
| Balsa | No | No | Yes | Yes | No | No | No |
| Becky! Internet Mail | Yes | No | No | No | No | No | No |
| Canary Mail | Yes | Yes | No | No | No | No | No |
| Citadel | No | Yes | Yes | Yes | Yes | No | No |
| Claws Mail | Yes | Yes | Yes | Yes | Yes | No | No |
| Courier | Yes | No | No | No | No | No | No |
| Elm | No | Yes | Yes | Yes | Yes | No | No |
| eM Client | Yes | Yes | No | No | No | No | No |
| EmailTray | Yes | No | No | No | No | No | No |
| Eudora | Yes | Yes | No | No | No | No | No |
| Evolution | No | No | Yes | Yes | Yes | No | No |
| Forté Agent | Yes | No | No | No | No | No | No |
| Geary | No | No | Yes | Yes | Yes | No | No |
| Gnus | Yes | Yes | Yes | Yes | Yes | Yes | No |
| GroupWise | Yes | Yes | Yes | Yes | No | No | No |
| Hiri | Yes | Yes | Yes | No | Yes | No | No |
| i.Scribe / InScribe | Yes | Yes | Yes | No | No | No | No |
| IBM Lotus Notes | Yes | Yes | Yes | No | Yes | No | No |
| IMP | Yes | Yes | Yes | Yes | Yes | No | No |
| KMail | No | Yes | Yes | Yes | Yes | No | No |
| Mailbird | Yes | Yes | No | No | No | No | No |
| Mailpile | Yes | Yes | Yes | Yes | Yes | No | No |
| mailx | No | No | Yes | Yes | Yes | No | No |
| Microsoft Entourage | No | Terminated (2008) | No | No | No | No | No |
| Microsoft Office Outlook | Yes | Yes | No | No | No | No | No |
| Mozilla Mail & Newsgroups | Terminated (1.7.13) | Terminated (1.7.13) | Terminated (1.7.13) | Terminated (1.7.13) | Terminated (1.7.13) | No | No |
| Mozilla Thunderbird | Yes | Yes | Yes | Yes | Yes | No | No |
| Mulberry | Yes | Yes | Yes | Yes | Yes | No | No |
| Mutt | Yes | Yes | Yes | Yes | Yes | Yes | No |
| Netscape Messenger | Terminated (4.80) | Terminated (4.80) | Terminated (4.80) | Terminated (4.80) | Terminated (4.80) | No | No |
| Netscape Messenger 9 | Terminated (9.0a1) | Terminated (9.0a1) | Terminated (9.0a1) | Terminated (9.0a1) | Terminated (9.0a1) | No | No |
| nmh / MH | No | Yes | Yes | Yes | Yes | No | No |
| Opera Mail | Yes | Yes | Yes | Yes | ? | No | No |
| Outlook Express | Included (up to XP) | No | No | No | No | No | No |
| Pegasus Mail | Yes | No | No | No | No | Yes | NetWare NLM |
| Pine | Yes | Yes | Yes | Yes | Yes | Terminated (3.96) | No |
| Pocomail | Yes | No | No | No | No | No | No |
| RoundCube | Yes | Yes | Yes | Yes | Yes | No | No |
| SeaMonkey Mail & Newsgroups | Yes | Yes | Yes | Yes | Yes | No | No |
| SquirrelMail | Yes | Yes | Yes | Yes | Yes | No | No |
| Sylpheed | Yes | Yes | Yes | Yes | Yes | No | No |
| The Bat! | Yes | No | No | No | No | No | No |
| Trojitá | Yes | Yes | Yes | Yes | Yes | No | MeeGo |
| Turnpike | Yes | No | No | No | No | No | No |
| Vivaldi | Yes | Yes | Yes | Yes | Yes | No | No |
| Windows Live Mail | Yes | No | No | No | No | No | No |
| Windows Mail | Included (Vista) | No | No | No | No | No | No |
| YAM | No | No | No | No | No | No | AmigaOS AROS MorphOS |
| Zimbra | Yes | Yes | Yes | Yes | Yes | No | No |
| Client | Microsoft Windows | macOS | Linux | BSD | Unix | DOS | Other |
* ↑ Development stopped in 2008
* 1 2 Packaging planned
* 1 2 Free Software project, source available.
* 1 2 Free Software porting tangible provided OS has web browser.

## Protocol support
### Communication and access protocol support

What email and related protocols and standards are supported by each client.
| Client | POP3 fetch all messages (RFC 1939) | POP3 selected by filter (RFC 1939) | POP3 selected by user (RFC 1939) | IMAP4 (RFC 3501) | SMTP (RFC 5321) | NNTP (RFC 3977) | LDAP v2 (RFC 4511) | LDAP v3 (RFC 4511) | EWS | IPv6 (RFC 2460) | MAPI |
| Alpine | Yes | Yes | Yes | Yes | Yes | Yes | Yes | Yes | ? | Yes | ? |
| Apple Mail | Yes | Yes | Yes | Yes | Yes | ? | Yes | Yes | ? | Yes | ? |
| Becky! Internet Mail | Yes | Yes | Yes | Yes | Yes | Yes | Yes | ? | ? | ? | ? |
| Canary Mail | No | No | No | Yes | Yes | No | No | No | Yes | Yes | No |
| Citadel | Yes | ? | ? | Yes | Yes | ? | ? | ? | ? | ? | ? |
| Claws Mail | Yes | Yes | Yes | Yes | Yes | Yes | Yes | Yes | ? | Yes | ? |
| Courier | Yes | Yes | Yes | Yes | Yes | No | Yes | Yes | ? | ? | ? |
| Elm | No | No | No | ? | ? | ? | ? | ? | ? | ? | ? |
| eM Client | Yes | Yes | Yes | Yes | Yes | No | No | No | Yes | Yes | No |
| EmailTray | Yes | No | No | Yes | Yes | No | No | No | No | No | No |
| Evolution | Yes | No | Yes | Yes | Yes | Yes | Yes | Yes | plug-in | ? | plug-in |
| Gnus | Yes | Yes | Yes | Yes | Yes | Yes | Yes | Yes | No | Yes | Plug-in |
| GroupWise | Yes | Yes | Yes | Yes | Yes | Yes | Yes | Yes | No | Yes | Yes |
| Hiri | No | No | No | No | No | No | Yes | Yes | Yes | Yes | No |
| i.Scribe / InScribe | Yes | No | Yes | Yes | Yes | No | Yes | Yes | No | No | Yes |
| HCL Notes | Yes | Yes | Yes | Yes | Yes | Yes | Yes | Yes | No | Yes | No |
| KMail | Yes | Yes | Yes | Yes | Yes | No | Yes | ? | ? | ? | ? |
| Mailbird | Yes | ? | ? | Yes | Yes | ? | Yes | Yes | ? | Yes | ? |
| Mailpile | Yes | No | No | Yes | Yes | ? | ? | ? | ? | ? | ? |
| Microsoft Entourage | Yes | ? | ? | Yes | Yes | Yes | No | Yes | Partial | ? | ? |
| Microsoft Entourage 2008, Web Services Edition | Yes | ? | ? | Yes | Yes | ? | ? | Yes | Yes | ? | ? |
| Microsoft Office Outlook | Yes | No | No | Yes | Yes | No | Yes | ? | Yes | Yes | Yes |
| Mozilla Mail & Newsgroups | Yes | ? | ? | ? | ? | Yes | ? | ? | ? | ? | ? |
| Mozilla Thunderbird | Yes | No | No | Yes | Yes | Yes | Partial | Partial | extensible | Yes | Yes |
| Mulberry | Yes | No | No | Yes | Yes | No | Yes | ? | ? | Yes | Yes |
| Mutt | Yes | No (possible with POP3 browser) | No (possible with POP3 browser) | Yes | Yes | No (slrn looks alike) | Partial (resolve real names through NSS) | ? | ? | Yes | ? |
| Netscape Messenger | Yes | ? | ? | Yes | ? | Yes | ? | ? | ? | ? | ? |
| Netscape Messenger 9 | Yes | ? | ? | Yes | ? | Yes | ? | ? | ? | ? | ? |
| nmh / MH | Yes | ? | ? | No | Yes | ? | ? | ? | No | ? | No |
| Opera Mail | Yes | No | Yes | Yes | Yes | Yes | No | No | ? | Yes | Yes |
| Outlook Express | Yes | No | No | Yes | Yes | Yes | Yes | ? | No | ? | No |
| Pegasus Mail | Yes | Yes | Yes | Yes | Yes | Yes | Yes | ? | ? | ? | ? |
| Pine | Yes | No | No | Yes | Yes | Yes | Yes | No | ? | ? | ? |
| Pocomail | Yes | Yes | Yes | Yes | Yes | No | No | No | ? | ? | ? |
| RoundCube | Yes | No | No | Yes | Yes | No | Yes | Yes | ? | ? | ? |
| SeaMonkey Mail & Newsgroups | Yes | No | No | Yes | Yes | Yes | Partial | ? | ? | Yes | ? |
| SquirrelMail | Yes | No | No | Yes | Yes | No | Yes | Yes | ? | ? | ? |
| Sylpheed | Yes | Yes | Yes | Yes | Yes | Yes | Yes | No | No | Yes | No |
| The Bat! | Yes | Yes | Yes | Yes | Yes | Yes | Yes | No | No | Yes | Yes |
| Trojitá | No | No | No | Yes | Yes | No | No | No | No | Yes | No |
| Turnpike | Yes | ? | ? | ? | Yes | Yes | ? | ? | ? | ? | ? |
| Vivaldi | Yes | ? | ? | Yes | Yes | No | ? | ? | ? | Yes |
| Windows Live Mail | Yes | No | No | Yes | Yes | Yes | Yes | ? | No | Yes | No |
| Windows Mail | Yes | No | No | Yes | Yes | ? | ? | ? | No | Yes | No |
| YAM | Yes | Yes | Yes | No | Yes | No | No | No | ? | ? | ? |
| Zimbra | Yes | No | No | Yes | Yes | No | Yes | Yes | ? | ? | ? |
| Client | POP3 fetch all messages (RFC 1939) | POP3 selected by filter (RFC 1939) | POP3 selected by user (RFC 1939) | IMAP4 (RFC 3501) | SMTP (RFC 5321) | NNTP (RFC 3977) | LDAP v2 (RFC 4511) | LDAP v3 (RFC 4511) | EWS | IPv6 (RFC 2460) | MAPI |

### Integration protocol support

| Client | IMSP | ACAP (RFC 2244) | RSS 0.91 Feeds | RSS 1.0 Feeds | RSS 2.0 Feeds | ATOM Feeds | iCalendar (RFC 5545) | MAPI/RPC | CalDAV (RFC 4791) | CardDAV (RFC 6352) |
| Alpine | ? | ? | ? | ? | ? | ? | ? | ? | ? | ? |
| Apple Mail | ? | ? | ? | ? | ? | ? | Yes | ? | Yes | Yes |
| Becky! Internet Mail | ? | ? | Yes | Yes | Yes | Yes | ? | ? | ? | ? |
| Canary Mail | No | No | No | No | No | No | No | No | No | No |
| Citadel | ? | ? | ? | ? | ? | ? | ? | ? | ? | ? |
| Claws Mail | ? | ? | No | Yes | Yes | Yes | Yes | ? | ? | ? |
| Courier | No | No | No | No | No | No | No | ? | ? | ? |
| Elm | ? | ? | ? | ? | ? | ? | ? | ? | ? | ? |
| eM Client | No | No | Yes | Yes | Yes | No | Yes | No | Yes | Yes |
| EmailTray | No | No | No | No | No | No | No | No | ? | ? |
| Eudora | No | Yes | No | No | No | No | No | ? | ? | ? |
| Evolution | No | No | No | No | No | No | Yes | Yes | Yes | Yes |
| Gnus | No | No | Yes | Yes | Yes | Yes | Yes | Yes | Yes | Yes |
| GroupWise | ? | No | ? | ? | ? | ? | Yes | ? | ? | ? |
| Hiri | No | No | No | No | No | No | No | No | No | No |
| i.Scribe / InScribe | No | No | No | No | No | No | No | Yes | ? | ? |
| IBM Lotus Notes | No | No | Yes | Yes | Yes | Yes | Yes | ? | ? | ? |
| KMail | ? | ? | Yes | Yes | Yes | Yes | Yes | ? | Yes | Yes |
| Mailpile | ? | ? | ? | ? | ? | ? | ? | ? | ? | ? |
| Microsoft Entourage | ? | ? | ? | ? | ? | ? | Yes | ? | ? | ? |
| Microsoft Office Outlook | ? | ? | Yes | Yes | Yes | Yes | Yes | Yes | No | No |
| Mozilla Mail & Newsgroups | ? | ? | ? | ? | ? | ? | ? | ? | ? | ? |
| Mozilla Thunderbird | No | No | Yes | Yes | Yes | Yes | Yes | Yes | Yes | Yes |
| Mulberry | Yes | Yes | No | No | No | No | Yes | ? | Yes | ? |
| Mutt | ? | ? | No | No | No | No | No | ? | ? | ? |
| Netscape Messenger | ? | ? | ? | ? | ? | ? | ? | ? | ? | ? |
| Netscape Messenger 9 | ? | ? | ? | ? | ? | ? | ? | ? | ? | ? |
| nmh / MH | ? | ? | ? | ? | ? | ? | ? | ? | ? | ? |
| Opera Mail | ? | ? | Yes | Yes | Yes | Yes | No | ? | No | No |
| Outlook Express | ? | ? | No | No | No | No | No | ? | No | No |
| Pegasus Mail | ? | ? | Yes | Yes | Yes | ? | ? | ? | ? | ? |
| Pine | No | No | No | No | No | No | No | ? | ? | ? |
| Pocomail | No | No | Yes | Yes | Yes | No | No | ? | ? | ? |
| SeaMonkey Mail & Newsgroups | No | No | Yes | Yes | Yes | Yes | Yes | ? | ? | ? |
| SquirrelMail | ? | ? | Yes | Yes | Yes | Yes | Yes | Yes | ? | ? |
| Sylpheed | No | No | No | No | No | No | No | No | ? | ? |
| The Bat! | No | No | Yes | Yes | Yes | Yes | No | Yes | ? | Yes |
| Trojitá | No | No | No | No | No | No | No | No | ? | ? |
| Turnpike | ? | ? | ? | ? | ? | ? | ? | ? | ? | ? |
| Windows Live Mail | ? | ? | Yes | Yes | Yes | Yes | No | ? | ? | ? |
| Windows Mail | ? | ? | ? | ? | ? | ? | ? | ? | ? | ? |
| YAM | No | No | No | No | No | No | No | ? | ? | ? |
| Zimbra | ? | ? | Yes | Yes | Yes | Yes | Yes | ? | ? | ? |
| Client | IMSP | ACAP (RFC 2244) | RSS 0.91 Feeds | RSS 1.0 Feeds | RSS 2.0 Feeds | ATOM Feeds | iCalendar (RFC 5545) | MAPI/RPC | CalDAV (RFC 4791) | CardDAV (RFC 6352) |
* ↑ Becky! requires FRNews or BkNews plugin installed for handling NNTP.
* 1 2 i.Scribe / InScribe requires a plugin to handle LDAP.
* ↑ KDE supports Newsgroups (NNTP) by the use of KNode
* 1 2 3 4 Pegasus Mail can convert Newsgroup messages and/or RSS feeds to emails through the use of free add-ons.
* ↑ Selective Download filters can skip/delete messages on POP3 server based on header (sender, recipient, subject, etc) information, this doesn't require to retrieve the full message body from the server.
* ↑ Message Dispatcher allows the user to decide which messages should be retrieved, deleted or skipped based on the header information (sender, recipient, subject, etc) displayed to the user.
* ↑ The Bat! requires MyGate plugin installed for handling NNTP.
* 1 2 3 4 Becky! requires BkBlogReader or BkRSSviewer or B.F.R or BkRssReader plugin installed for handling RSS and ATOM.
* 1 2 3 RSSyl plugin is required to read RSS and ATOM in Claws Mail.
* ↑ vCalendar plugin is required to handle iCalendar in Claws Mail.
* 1 2 3 The evolution-rss plugin (provided as a separate package by many distributions provides the RSS functionality in Evolution.
* ↑ Studio Blog Reader is one RSS reader application for IBM Lotus Notes. IBM Lotus Notes version 8.x introduced a native RSS reader.
* 1 2 3 4 KDE supports feeds by the use of Akregator
* ↑ KDE supports iCal by the use of KOrganizer
* 1 2 3 4 Support of feeds is available in Microsoft Office Outlook 2007. Earlier versions require RSSPopper plug-in.
* ↑ Microsoft Outlook support of iCalendar varies by version.
* 1 2 iCalendar is supported with an extension.
* ↑ Mozilla Thunderbird only supports SimpleMAPI.
* 1 2 3 4 The Bat! versions prior to 6.3 required rss2mail or rss2pop3 plugin installed for handling RSS and ATOM. The Bat! versions 6.3 and later have built-in support for RSS.

### Authentication support

| Client | Regular | Regular | MSN (NTLM) browser login | Compuserve (RPA) | MD5 APOP | CRAM-HMAC | CRAM-HMAC | CRAM-HMAC | DIGEST-MD5 | SCRAM | with hardware token PKCS#11 | Biometric | SMTP Auth | X.509 Client certificate | OAuth |
| Client | LOGIN | PLAIN | MSN (NTLM) browser login | Compuserve (RPA) | MD5 APOP | MD5 | SHA1 | RIPEMD | DIGEST-MD5 | SCRAM | with hardware token PKCS#11 | Biometric | SMTP Auth | X.509 Client certificate | OAuth |
| Alpine | Yes | Yes | No | No | No | Yes | No | No | No | ? | No | No | Yes | No | ? |
| Apple Mail | Yes | Yes | No | No | ? | ? | ? | ? | ? | ? | ? | Yes | Yes | Yes | Yes |
| Becky! Internet Mail | Yes | Yes | Yes | ? | Yes | Yes | ? | ? | ? | ? | ? | ? | Yes | Yes | ? |
| Canary Mail | Yes | Yes | No | No | No | Yes | No | No | Yes | Yes | No | Yes | Yes | No | Yes |
| Citadel | ? | ? | ? | ? | ? | ? | ? | ? | ? | ? | ? | ? | ? | ? | ? |
| Claws Mail | Yes | Yes | ? | ? | Yes | Yes | ? | ? | Yes | Yes | No | ? | Yes | No | Yes |
| Courier | Yes | Yes | Yes | No | Yes | Yes | Yes | No | Yes | ? | No | No | Yes | Yes | ? |
| Elm | ? | ? | ? | ? | ? | ? | ? | ? | ? | ? | ? | ? | ? | ? | ? |
| eM Client | Yes | Yes | Yes | No | No | Yes | No | No | Yes | ? | No | No | Yes | No | Yes |
| EmailTray | Yes | Yes | ? | ? | Yes | Yes | Yes | No | ? | ? | No | No | Yes | No | ? |
| Eudora | Yes | Yes | Yes | Yes | Yes | Yes | No | No | No | ? | No | No | No | ? | ? |
| Evolution | Yes | Yes | Yes | No | Yes | Yes | No | No | Yes | ? | No | No | Yes | No | Yes |
| Gnus | Yes | Yes | ? | ? | Yes | Yes | Yes | ? | Yes | ? | ? | ? | Yes | ? | ? |
| GroupWise | ? | ? | ? | ? | ? | ? | ? | ? | ? | ? | ? | ? | ? | ? | ? |
| Hiri | Yes | Yes | Yes | No | No | No | No | No | No | ? | No | No | No | No | Yes |
| i.Scribe / InScribe | Yes | Yes | Yes | No | Yes | No | No | No | No | ? | No | No | Yes | No | Yes |
| IBM Lotus Notes | Yes | ? | Yes | No | No | No | ? | ? | ? | ? | Yes | No | Yes | ? | ? |
| KMail | Yes | Yes | Yes | No | Yes | Yes | No | No | Yes | ? | No | No | Yes | Yes | ? |
| Mailpile | ? | ? | ? | ? | ? | ? | ? | ? | ? | ? | ? | ? | ? | ? | ? |
| Microsoft Entourage | Yes | No | Yes | ? | ? | Yes | ? | ? | ? | ? | Yes | ? | Yes | Yes | ? |
| Microsoft Office Outlook | Yes | No | Yes | No | No | No | No | No | No | ? | No | No | Yes | No | ? |
| Mozilla Mail & Newsgroups | Yes | ? | ? | Yes | ? | Yes | ? | ? | ? | ? | ? | ? | ? | ? | ? |
| Mozilla Thunderbird | Yes | Yes | Yes | No | Yes | Yes | No | No | No | ? | Yes | No | Yes | Yes | Yes |
| Mulberry | Yes | Yes | Yes | No | No | Yes | No | No | Yes | ? | No | No | Yes | Yes | ? |
| Mutt | Yes | Yes | Yes | ? | Yes | Yes | No | No | Yes | ? | No | No | 1.5.15 | Yes | 1.10.1 |
| Netscape Messenger | ? | ? | ? | ? | ? | ? | ? | ? | ? | ? | ? | ? | ? | ? | ? |
| Netscape Messenger 9 | ? | ? | ? | ? | ? | ? | ? | ? | ? | ? | ? | ? | ? | ? | ? |
| nmh / MH | ? | ? | ? | ? | ? | ? | ? | ? | ? | ? | ? | ? | ? | ? | ? |
| Opera Mail | Yes | Yes | No | No | Yes | Yes | No | ? | ? | ? | No | No | Yes | Yes | ? |
| Outlook Express | Yes | No | Yes | No | No | No | No | No | No | ? | No | No | Yes | No | ? |
| Pegasus Mail | Yes | ? | No | No | Yes | No | No | No | No | ? | No | No | Yes | Yes | ? |
| Pine | Yes | Yes | No | No | No | Yes | No | No | No | ? | No | No | Yes | No | ? |
| Pocomail | ? | ? | ? | ? | ? | ? | ? | ? | ? | ? | ? | ? | ? | ? | ? |
| RoundCube | Yes | Yes | ? | ? | Yes | Yes | Yes | ? | Yes | ? | Yes | ? | Yes | ? | ? |
| SeaMonkey Mail & Newsgroups | Yes | Yes | Yes | No | Yes | Yes | No | No | No | ? | Yes | No | Yes | Yes | ? |
| SquirrelMail | Yes | Yes | ? | ? | Yes | Yes | Yes | ? | Yes | ? | Yes | ? | Yes | ? | ? |
| Sylpheed | Yes | Yes | No | No | Yes | Yes | No | No | No | ? | No | No | Yes | No | No |
| The Bat! | Yes | Yes | Yes | Yes | Yes | Yes | No | No | No | ? | Yes | Yes | Yes | No | Yes |
| Trojitá | Yes | No | No | No | No | No | No | No | No | ? | No | No | Yes | No | ? |
| Turnpike | ? | ? | ? | ? | ? | ? | ? | ? | ? | ? | ? | ? | ? | ? | ? |
| Windows Live Mail | Yes | No | Yes | No | Yes | No | No | No | No | ? | No | No | No | No | No |
| Windows Mail | ? | ? | ? | ? | ? | ? | ? | ? | ? | ? | ? | ? | ? | ? | Yes |
| YAM | Yes | Yes | ? | ? | Yes | Yes | ? | ? | ? | ? | ? | ? | Yes | AmiSSL | ? |
| Zimbra | Yes | Yes | ? | ? | Yes | Yes | ? | ? | ? | ? | Yes | ? | Yes | ? | ? |
| Client | Regular | Regular | MSN (NTLM) browser login | Compuserve (RPA) | MD5 APOP | CRAM-HMAC | CRAM-HMAC | CRAM-HMAC | DIGEST-MD5 | SCRAM | with hardware token PKCS#11 | Biometric | SMTP Auth | SSL/TLS Client Certificate | OAUTH |
| Client | LOGIN | PLAIN | MSN (NTLM) browser login | Compuserve (RPA) | MD5 APOP | MD5 | SHA1 | RIPEMD | DIGEST-MD5 | SCRAM | with hardware token PKCS#11 | Biometric | SMTP Auth | SSL/TLS Client Certificate | OAUTH |
* 1 2 Description: RFC 1734
* 1 2 Description: RFC 2195
* 1 2 Description: RFC 2554
* ↑ Minimum Mac OS version 10.11. Minimum iOS version 11.
* 1 2 Professional Edition.
* ↑ Windows 10 required.
* ↑ Zimbra Desktop supports SMTP auth, not sure about collaboration suite

### SSL and TLS support

| Client | Secure POP3 | Secure POP3 | Secure IMAP4 | Secure IMAP4 | Secure SMTP | Secure SMTP | Secure NNTP | Secure NNTP | Secure LDAP | Secure LDAP | SNI | OCSP | CRL |
| Client | SSL | TLS | SSL | TLS | SSL | TLS | SSL | TLS | SSL | TLS | SNI | OCSP | CRL |
| Alpine | Yes | Yes | Yes | Yes | Yes | Yes | Yes | Yes | ? | Yes | ? | ? | ? |
| Apple Mail | Yes | Yes | Yes | Yes | Yes | Yes | ? | ? | ? | ? | ? | ? | ? |
| Becky! Internet Mail | Yes | Yes | Yes | Yes | Yes | Yes | ? | ? | ? | ? | ? | ? | ? |
| Canary Mail | No | No | Yes | Yes | Yes | Yes | No | No | No | No | No | No | No |
| Citadel | ? | ? | ? | ? | ? | ? | ? | ? | ? | ? | ? | ? | ? |
| Claws Mail | Yes | Yes | Yes | Yes | Yes | Yes | Yes | Yes | Yes | Yes | ? | ? | Yes |
| Courier | No | No | No | No | No | No | No | No | No | No | No | No | No |
| Elm | ? | ? | ? | ? | ? | ? | ? | ? | ? | ? | ? | ? | ? |
| eM Client | Yes | Yes | Yes | Yes | Yes | Yes | No | No | No | No | ? | No | Yes |
| EmailTray | Yes | Yes | Yes | Yes | Yes | Yes | No | No | No | No | ? | No | No |
| Eudora | Yes | Yes | Yes | Yes | Yes | Yes | No | No | Yes | Yes | ? | ? | ? |
| Evolution | Yes | Yes | Yes | Yes | Yes | Yes | Yes | Yes | Yes | Yes | ? | No | No |
| Gnus | Yes | Yes | Yes | Yes | Yes | Yes | Yes | Yes | ? | ? | ? | ? | ? |
| GroupWise | ? | ? | ? | ? | ? | ? | ? | ? | ? | ? | ? | ? | ? |
| Hiri | No | No | No | No | No | No | No | No | No | No | No | No | No |
| i.Scribe / InScribe | Yes | Yes | Yes | No | Yes | Yes | No | No | No | No | ? | No | No |
| IBM Lotus Notes | Yes | Yes | Yes | ? | Yes | Yes | Yes | ? | Yes | ? | ? | Yes | Yes |
| KMail | Yes | Yes | Yes | Yes | Yes | Yes | No | No | ? | ? | ? | ? | ? |
| Mailpile | ? | Yes | ? | Yes | ? | ? | ? | ? | ? | ? | ? | ? | ? |
| Microsoft Entourage | Yes | ? | Yes | ? | Yes | ? | Yes | ? | Yes | ? | ? | ? | ? |
| Microsoft Office Outlook | Yes | No | Yes | Yes | Yes | Yes | ? | ? | ? | ? | ? | ? | ? |
| Mozilla Mail & Newsgroups | ? | ? | ? | ? | ? | ? | ? | ? | ? | ? | ? | ? | ? |
| Mozilla Thunderbird | Yes | Yes | Yes | Yes | Yes | Yes | Yes | Yes | Yes | No | Yes | Yes | Yes |
| Mulberry | Yes | Yes | Yes | Yes | Yes | Yes | No | No | Yes | Yes | ? | ? | ? |
| Mutt | Yes | Yes | Yes | Yes | 1.5.15 | 1.5.15 | ? | ? | ? | ? | ? | ? | ? |
| Netscape Messenger | ? | ? | ? | ? | ? | ? | ? | ? | ? | ? | ? | ? | ? |
| Netscape Messenger 9 | ? | ? | ? | ? | ? | ? | ? | ? | ? | ? | ? | ? | ? |
| nmh / MH | ? | ? | ? | ? | ? | ? | ? | ? | ? | ? | ? | ? | ? |
| Opera Mail | Yes | Partial | Yes | Partial | Yes | Partial | Yes | No | — | — | ? | Yes | Yes |
| Outlook Express | Yes | Yes | Yes | Yes | Yes | Yes | ? | ? | ? | ? | ? | ? | ? |
| Pegasus Mail | Yes | Yes | Yes | Yes | Yes | Yes | ? | ? | Yes | ? | ? | ? | ? |
| Pine | Yes | Yes | Yes | Yes | Yes | Yes | Yes | Yes | No | No | ? | ? | ? |
| Pocomail | ? | ? | ? | ? | ? | ? | ? | ? | ? | ? | ? | ? | ? |
| RoundCube | Yes | Yes | Yes | Yes | Yes | Yes | No | No | Yes | Yes | ? | ? | ? |
| SeaMonkey Mail & Newsgroups | Yes | Yes | Yes | Yes | Yes | Yes | Yes | Yes | Yes | Yes | Yes | Yes | Yes |
| SquirrelMail | Yes | Yes | Yes | Yes | Yes | Yes | No | No | Yes | Yes | ? | ? | ? |
| Sylpheed | Yes | Yes | Yes | Yes | Yes | Yes | Yes | Yes | ? | ? | ? | ? | ? |
| The Bat! | Yes | Yes | Yes | Yes | Yes | Yes | No | No | No | No | Yes | Yes | Yes |
| Trojitá | ? | ? | Yes | Yes | Yes | Yes | ? | ? | ? | ? | ? | Yes (system) | Yes (system) |
| Turnpike | ? | ? | ? | ? | ? | ? | ? | ? | ? | ? | ? | ? | ? |
| Windows Live Mail | Yes | No | Yes | No | Yes | No | ? | ? | ? | ? | ? | ? | ? |
| Windows Mail | Yes | No | Yes | ? | Yes | ? | ? | ? | ? | ? | ? | ? | ? |
| YAM | Yes | Yes | No | No | ? | ? | ? | ? | ? | ? | ? | ? | ? |
| Zimbra | Yes | Yes | Yes | Yes | Yes | Yes | Yes | Yes | Yes | Yes | ? | ? | ? |
| Client | Secure POP3 | Secure POP3 | Secure IMAP4 | Secure IMAP4 | Secure SMTP | Secure SMTP | Secure NNTP | Secure NNTP | Secure LDAP | Secure LDAP | SNI | OCSP | CRL |
| Client | SSL | TLS | SSL | TLS | SSL | TLS | SSL | TLS | SSL | TLS | SNI | OCSP | CRL |
* 1 2 Online Certificate Status Protocol - Description: RFC 2560
* 1 2 Certificate revocation list - Description: RFC 3280
* 1 2 3 4 Description: RFC 2595
* 1 2 Description: RFC 2487
* 1 2 3 Opera Mail does not support STARTTLS command on special ports, like 995 for pop3 connection
* 1 2 Since version 4.2, The Bat! supports two modes of X.509 certificate handling: Internal Implementation and via Microsoft CryptoAPI. CRLs and OCSP are only supported in the latter mode during TLS connections.

## Features

Information on what features each of the clients support.

### General features

For all of these clients, the concept of "HTML support" does not mean that they can process the full range of HTML that a web browser can handle. Almost all email readers limit HTML features, either for security reasons, or because of the nature of the interface. CSS and JavaScript can be especially problematic.
| Client | HTML email | UTF-8 support | Image blocking | Junk filtering | Junk filtering | Phishing filtering | Thread view | Conversation view | PGP support | PGP support | S/MIME support | S/MIME support | S/MIME support | S/MIME support |
| Client | HTML email | UTF-8 support | Image blocking | local | server- side | Phishing filtering | Thread view | Conversation view | inline | PGP/MIME or OpenPGP | protocol | OCSP | CRL | certificates on tokens, smartcards support |
| Alpine | Read only | Yes | Yes | ? | ? | ? | Yes | ? | Yes | ? | Yes | ? | ? | ? |
| Apple Mail | Yes | Yes | Yes | Yes | Yes | ? | Yes | Yes | No | No | Yes | Yes | Yes | No |
| Becky! Internet Mail | Yes | Yes | Yes | No | No | No | Yes | No | Yes | ? | Yes | ? | ? | ? |
| Canary Mail | Yes | Yes | Yes | ? | Yes | ? | Yes | Yes | Yes | Yes | No | No | No | No |
| Citadel | Yes | Yes | No | Yes | ? | ? | No | ? | ? | ? | ? | ? | ? |
| Claws Mail | Read-only | Yes | Yes | Yes | Yes | Yes | Yes | ? | Yes | Yes | Yes | ? | Yes | Yes |
| Courier | Yes | No | No | Yes | Yes | ? | No | ? | ? | ? | ? | ? | ? | ? |
| Elm | ? | ? | ? | ? | ? | ? | ? | ? | ? | ? | ? | ? | ? | ? |
| eM Client | Yes | Yes | Yes | Yes | Yes | Yes | No | Yes | Yes | Yes | Yes | No | Yes | Yes |
| EmailTray | Yes | Yes | Yes | No | Yes | ? | No | No | No | No | No | No | No | No |
| Eudora | Yes | No | Yes | Pro only | Pro only | ? | Yes | No | Yes | Yes | Yes | ? | ? | ? |
| Evolution | Yes | Yes | Yes | Yes | ? | No | Yes | No | Yes | Yes | Yes | ? | ? | ? |
| Gnus | Yes | Yes | Yes | Yes | Yes | ? | Yes | ? | Yes | Yes | Yes | ? | ? | Yes |
| GroupWise | Yes | Yes | Yes | Yes | ? | ? | Yes | ? | ? | ? | ? | ? | ? | ? |
| Hiri | Yes | Yes | Yes | Yes | Yes | ? | Yes | Yes | Yes | No | No | No | No | No |
| i.Scribe / InScribe | Read-only | Yes | Yes | Yes | No | ? | Yes | ? | Yes | No | No | No | No | No |
| HCL Notes | Yes | Yes | Yes | Yes | Yes | Yes | Yes | ? | Yes | Yes (4.1.2+) | Yes | Yes | Yes | Yes |
| KMail | Yes | Yes | Yes | Yes | ? | ? | Yes | Yes | Yes (with GPG) | Yes (1.5+, with GPGME) | Yes | Yes | Yes | ? |
| Mailbird | Yes | Yes | Yes | Yes | Yes | Yes | Yes | Yes | ? | No | No | No | No | No |
| Mailpile | ? | Yes | ? | ? | ? | ? | ? | Yes | ? | Yes | ? | ? | ? | ? |
| Microsoft Entourage | Yes | Yes | Yes | Yes | Yes | Yes | ? | ? | ? | Yes | Yes | ? | ? | Yes |
| Microsoft Office Outlook | Yes | Yes | Yes | Yes | Yes | Yes | Yes | Yes (2010+) | No | No | Yes | ? | Yes | Yes |
| Mozilla Mail & Newsgroups | ? | ? | ? | ? | ? | ? | ? | ? | ? | ? | ? | ? | ? | ? |
| Mozilla Thunderbird | Yes | Yes | Yes | Yes | Yes | Yes | Yes | Yes | Yes | Yes | Yes | Yes | ? | Yes |
| Mulberry | Yes | Yes | Yes | No | Yes | ? | Yes | ? | Yes | Yes | Yes | ? | ? | ? |
| Mutt | Read-only | Yes | Yes (no support for images) | Yes | ? | ? | Yes | Yes | Yes | Yes | Yes | ? | Yes (with GPGME) | ? |
| Netscape Messenger | ? | ? | ? | ? | ? | ? | ? | ? | ? | ? | ? | ? | ? | ? |
| Netscape Messenger 9 | ? | ? | ? | ? | ? | ? | ? | ? | ? | ? | ? | ? | ? | ? |
| nmh / MH | ? | ? | ? | ? | ? | ? | ? | ? | ? | ? | ? | ? | ? | ? |
| Opera Mail | Yes | Yes | Yes | Yes | Yes | No | Yes | No | No | No | No | No | No | No |
| Outlook Express | Yes | Yes | Yes | No | ? | ? | Yes | ? | Yes | No | Yes | ? | ? | ? |
| Pegasus Mail | Yes | Yes | Yes | Yes | Yes | Yes | Yes | ? | Yes | Yes (sending is broken) | ? | No | No | No |
| Pine | Read-only | Yes | Yes | No | ? | ? | Yes | ? | Yes (with Pine Privacy Guard) | No | Yes | ? | ? | ? |
| Pocomail | Yes | Yes | Yes | Yes | Yes | ? | ? | ? | ? | ? | ? | ? | ? | ? |
| RoundCube | Yes | Yes | Yes | Yes | Yes | Yes (depends on antivirus) | Yes | ? | ? | Yes | Yes | ? | ? | ? |
| SeaMonkey Mail & Newsgroups | Yes | Yes | Yes | Yes | ? | Yes | Yes | ? | Yes | Yes | Yes | Yes | ? | Yes |
| SquirrelMail | Yes | Yes | Yes | Yes | Yes | Yes (depends on antivirus) | Yes | ? | ? | Yes | Yes | ? | ? | ? |
| Sylpheed | No | Yes | Yes | Yes | ? | ? | Yes | ? | No | Yes | ? | ? | ? | ? |
| The Bat! | Yes | Yes | Yes | Yes | Yes | ? | Yes | ? | Yes | Yes | Yes | Partial | Partial | Yes |
| Trojitá | Read only | Yes | Yes | No | Yes | No | Yes | Yes | No | Read only | Read only | Read only | Read only | Read only |
| Turnpike | Read-only | ? | ? | ? | ? | ? | ? | ? | ? | ? | ? | ? | ? | ? |
| Windows Live Mail | Yes | Yes | Yes | Yes | Yes | Yes | Yes | Yes | Yes | ? | Yes | ? | ? | ? |
| Windows Mail | Yes | Yes | ? | Yes | ? | ? | ? | ? | ? | ? | ? | ? | ? | ? |
| YAM | ? | Yes | ? | Yes | ? | ? | No | No | Yes | ? | ? | ? | ? | ? |
| Zimbra | Yes | Yes | Yes | Yes | Yes | Yes (depends on antivirus) | Yes | ? | ? | No | ? | ? | ? |
| Client | HTML email | UTF-8 support | Image blocking | Junk filtering | Junk filtering | Phishing filtering | Thread view | Conversation view | PGP support | PGP support | S/MIME support | S/MIME support | S/MIME support | S/MIME support |
| Client | HTML email | UTF-8 support | Image blocking | local | server- side | Phishing filtering | Thread view | Conversation view | inline | PGP/MIME or OpenPGP | protocol | OCSP | CRL | certificates on tokens, smartcards support |
* ↑ Citadel plugs Mail into SpamAssassin
* 1 2 Eudora requires a plugin to handle PGP.
* ↑ First release 6.0 (September 2003), enhancements introduced in release 7.0 (August 2005)
* ↑ Although Thunderbird supports UTF-8, its handling of line wraps causes problems with long lines of text that don't contain spaces, which essentially makes it unusable for certain languages (e.g. Chinese, Japanese, Korean)
* ↑ Mozilla Thunderbird adds this feature in Thunderbird 1.5.0.4
* 1 2 3 Using PGP in Thunderbird before version 78 requires Enigmail.
* 1 2 3 PGP/GPG and S/MIME support require a free (included) plugin.
* ↑ Using PGP in Outlook Express requires a plugin.
* ↑ Outlook Express does not display PGP/MIME signed messages.
* ↑ Sylpheed has some limited ability to show HTML email. It can show the plain text that's left after stripping away all the HTML tags. Sylpheed has no ability to compose HTML.
* ↑ The Bat is not able to display inline images.
* 1 2 3 The Bat! supports two modes of S/MIME: Internal Implementation and via Microsoft CryptoAPI. CRLs and OCSP are only supported in the latter mode. Internal implementation only supports Aladdin eToken Pro or Rainbow iKey1000 tokens and can import certificates (from PKCS#12/PFX format) which were created outside The Bat!. CryptoAPI supports any kind of tokens and smart cards which have a corresponding Cryptographic Service Provider installed.

### Messages features

| Client | Label messages | Label messages | Label messages | Label messages | Reformat received messages | Reformat received messages | Bi-directional text support | Composing messages | Composing messages | Composing messages | Native images preview | Native images preview | Native images preview | Native images preview | Native images preview | Postpone / scheduled message sending | Native documents preview | Native documents preview | Native documents preview | Native documents preview | Native documents preview | Native documents preview | Native documents preview |
| Client | with colors | with flag | antidelete | add note | edit headers (e.g., Subject) | forced recode | Bi-directional text support | Spell checking | Signatures | Bottom-posts replies | jpeg | gif | bmp | png | others | Postpone / scheduled message sending | txt | pdf | doc | xls | odt | ods | others |
| Alpine | Yes | Yes | ? | ? | ? | ? | ? | Yes | Yes | ? | ? | ? | ? | ? | ? | Yes | Yes | ? | ? | ? | ? | ? | ? |
| Becky! Internet Mail | Yes | Yes | ? | Yes | Yes | Yes | ? | Yes | Yes | Yes | Yes | Yes | Yes | Yes | ? | ? | ? | ? | ? | ? | ? | ? | ? |
| Canary Mail | ? | ? | No | No | No | No | Yes | Yes | Yes | Yes | Yes | Yes | Yes | Yes | Yes | No | Yes | Yes | Yes | Yes | Yes | No | Yes |
| Citadel | ? | ? | ? | ? | ? | ? | ? | ? | ? | ? | ? | ? | ? | ? | ? | ? | ? | ? | ? | ? | ? | ? | ? |
| Claws Mail | Yes | Yes | Yes | No | Yes | Yes | Yes | Yes | Yes | Yes | Yes | Yes | Yes | Yes | ? | Yes | Yes | with a plugin | ? | ? | ? | ? | ? |
| Courier | Yes | Yes | No | No | Yes | ? | ? | Yes | Yes | ? | No | No | No | No | No | Yes | ? | No | No | No | No | No | ? |
| Elm | ? | ? | ? | ? | ? | ? | ? | ? | ? | ? | ? | ? | ? | ? | ? | ? | ? | ? | ? | ? | ? | ? | ? |
| eM Client | Yes | Yes | No | Yes | Yes | No | Yes | Yes | Yes | No | Yes | Yes | Yes | Yes | Yes | Yes | ? | Yes | ? | ? | ? | ? | ? |
| EmailTray | Yes | No | No | No | No | No | ? | Yes | Yes | Yes | Yes | Yes | Yes | Yes | ? | No | Yes | Yes | Yes | Yes | No | No | ? |
| Eudora | Yes | Yes | No | No | Yes | ? | ? | Yes | Yes | ? | Yes | Yes | Yes | Yes | QuickTime | Yes | ? | ? | ? | ? | ? | ? | ? |
| Evolution | Yes | Yes | ? | ? | No | ? | Yes | Yes | Yes | ? | Yes | Yes | Yes | Yes | ? | ? | ? | ? | ? | ? | ? | ? | ? |
| Gnus | Yes | Yes | Yes | ? | ? | ? | ? | Yes | Yes | Yes | Yes | Yes | Yes | Yes | XPM | Yes | ? | ? | ? | ? | ? | ? | ? |
| GroupWise | Yes | Yes | Yes | Yes | Yes | ? | ? | Yes | Yes | Yes | Yes | Yes | Yes | Yes | ? | Yes | Yes | Yes | Yes | Yes | Yes | Yes | ? |
| Hiri | Yes | Yes | No | Yes | No | No | No | Yes | No | Yes | Yes | Yes | Yes | Yes | Yes | No | No | No | No | No | No | No | No |
| i.Scribe / InScribe | Yes | No | No | Yes | No | No | No | Yes | Yes | Yes | Yes | Yes | Yes | Yes | ICO, TIFF | Yes | No | No | No | No | No | No | No |
| HCL Notes | Yes | Yes | ? | ? | Yes | ? | ? | Yes | Yes | ? | Yes | Yes | Yes | No | CGM, Lotus PIC, PCX, TIFF | ? | Yes | Yes | Yes | Yes | ? | ? | ? |
| KMail | Yes | Yes | No | Yes | ? | ? | ? | Yes | Yes | ? | Yes | Yes | Yes | Yes | ? | ? | ? | ? | ? | ? | ? | ? | ? |
| Mailbird | Yes | Yes | ? | Yes | ? | ? | ? | Yes | Yes | Yes | Yes | Yes | Yes | Yes | ? | Yes | Yes | Yes | Yes | Yes | No | No | ? |
| Mailpile | ? | ? | ? | ? | ? | ? | ? | ? | ? | ? | ? | ? | ? | ? | ? | ? | ? | ? | ? | ? | ? | ? | ? |
| Microsoft Entourage | Yes | Yes | ? | Yes | ? | ? | ? | Yes | Yes | ? | Yes | Yes | ? | Yes | ? | ? | ? | Yes | ? | ? | ? | ? | ? |
| Microsoft Office Outlook | Yes | Yes | No | Yes | Yes | ? | ? | Yes | Yes | No | Yes | Yes | Yes | Yes | ? | Yes | Yes | with a plugin | Yes | Yes | 2010 | 2010 | PowerPoint |
| Mozilla Mail & Newsgroups | ? | ? | ? | ? | ? | ? | ? | ? | ? | ? | ? | ? | ? | ? | ? | ? | ? | ? | ? | ? | ? | ? | ? |
| Mozilla Thunderbird | Yes | Yes | ? | ? | with a plugin | ? | ? | Yes | Yes | Yes | Yes | Yes | Yes | Yes | ICO | Yes | Yes | Yes | No | No | No | No | No |
| Mulberry | ? | Yes | ? | ? | ? | ? | ? | Yes | Yes | ? | No | No | No | No | No | ? | ? | ? | ? | ? | ? | ? | ? |
| Mutt | Yes | Yes | No | No | Yes | ? | ? | Yes | Yes | ? | No | No | No | No | No | postpone | ? | ? | ? | ? | ? | ? | ? |
| Netscape Messenger | ? | ? | ? | ? | ? | ? | ? | ? | ? | ? | ? | ? | ? | ? | ? | ? | ? | ? | ? | ? | ? | ? | ? |
| Netscape Messenger 9 | ? | ? | ? | ? | ? | ? | ? | ? | ? | ? | ? | ? | ? | ? | ? | ? | ? | ? | ? | ? | ? | ? | ? |
| nmh / MH | ? | ? | ? | ? | ? | ? | ? | ? | ? | ? | ? | ? | ? | ? | ? | ? | ? | ? | ? | ? | ? | ? | ? |
| Opera Mail | Yes | Yes | No | No | ? | ? | Yes | Yes | Yes | ? | Yes | Yes | Yes | Yes | APNG, ICO, SVG, WBMP, XBM, WebP | No | No | No | No | No | No | No | No |
| Outlook Express | No | Yes | No | No | ? | ? | ? | Yes | Yes | ? | Yes | Yes | Yes | Yes | ICO, art | ? | ? | ? | ? | ? | ? | ? | ? |
| Pegasus Mail | Yes | Yes | Yes | Yes | in index | No | No | Yes | Yes | No | Yes | Yes | Yes | Yes | TIFF | — | Yes | No | No | No | No | No | RTF, HTML |
| Pine | Yes | Yes | ? | ? | No | with a patch | ? | Yes | Yes | ? | No | No | No | No | No | ? | ? | ? | ? | ? | ? | ? | ? |
| Pocomail | Yes | Yes | ? | Yes | ? | ? | ? | Yes | Yes | ? | Yes | Yes | Yes | Yes | ? | ? | ? | ? | ? | ? | ? | ? | ? |
| RoundCube | Yes | Yes | Yes | Yes | ? | ? | Yes | Yes | Yes | ? | Yes | Yes | Yes | Yes | ? | ? | Yes | Yes | Yes | Yes | Yes | Yes | ? |
| SeaMonkey Mail & Newsgroups | Yes | Yes | No | No | ? | ? | ? | Yes | Yes | ? | Yes | Yes | Yes | Yes | ? | ? | ? | ? | ? | ? | ? | ? | ? |
| SquirrelMail | Yes | Yes | Yes | Yes | ? | ? | Yes | Yes | Yes | ? | Yes | Yes | Yes | Yes | ? | ? | Yes | Yes | Yes | Yes | Yes | Yes | ? |
| Sylpheed | Yes | Yes | No | No | ? | ? | ? | Yes | Yes | ? | Yes | Yes | Yes | Yes | ? | ? | Yes | No | No | No | No | No | ? |
| The Bat! | Yes | Yes | Yes | Yes | No | No | No | Yes | Yes | Yes | Yes | Yes | Yes | Yes | ICO, emf | Yes | Yes | No | No | No | No | No | No |
| Trojitá | No | Yes | ? | ? | No | No | Yes | No | Yes | Yes | Yes | Yes | Yes | Yes | Yes | Yes | Yes | No | No | No | No | No | Yes |
| Turnpike | Yes | ? | ? | No | ? | ? | ? | Yes | Yes | ? | Yes | Yes | Yes | No | ? | ? | ? | ? | ? | ? | ? | ? | ? |
| Windows Live Mail | No | Yes | No | No | ? | ? | ? | Yes | Yes | ? | Yes | Yes | Yes | Yes | ? | ? | ? | ? | ? | ? | ? | ? | ? |
| Windows Mail | ? | ? | ? | ? | ? | ? | ? | ? | ? | ? | ? | ? | ? | ? | ? | ? | ? | ? | ? | ? | ? | ? | ? |
| YAM | No | No | No | No | No | No | No | Yes | Yes | Yes | Yes | Yes | Yes | Yes | Yes | Yes | Yes | Yes | Yes | Yes | Yes | Yes | Yes |
| Zimbra | Yes | Yes | Yes | Yes | ? | ? | ? | Yes | Yes | ? | Yes | Yes | Yes | Yes | ? | ? | ? | ? | ? | ? | ? | ? | ? |
| Client | Label messages | Label messages | Label messages | Label messages | Reformat received messages | Reformat received messages | Bi-directional text support | Composing messages | Composing messages | Composing messages | Native images preview | Native images preview | Native images preview | Native images preview | Native images preview | Postpone/?scheduled message sending | Native documents preview | Native documents preview | Native documents preview | Native documents preview | Native documents preview | Native documents preview | Native documents preview |
| Client | with colors | with flag | antidelete | add note | edit headers (e.g., Subject) | forced recode | Bi-directional text support | Spell checking | Signatures | Bottom-posts replies | jpeg | gif | bmp | png | others | Postpone/?scheduled message sending | txt | pdf | doc | xls | odt | ods | others |
* 1 2 It's a frequent problem for people dealing with Cyrillic/Russian in email messages that the message is not encoded in the encoding declared in its headers and thus can't be read. With such a message (with a wrong declaration of the encoding), it well might be the case that it passed through several incorrect recoding stages while it was being sent and delivered; thus it's not possible to correctly render it and read it if one uses the common type of the interface for choosing the encoding (such as the menu in Mozilla Firefox). An example of such a complex case of a wrongly declared encoding: a message was entered through a webform in the windows-1251 encoding, but the web interface incorrectly assumed that it was in latin-1; based on this assumption, it performed the recoding from latin-1 to utf-8. The result of this operation cannot be correctly decoded through the common encoding-selection interface; it can only be decoded through a two-stage recoding: first from utf-8 to latin-1, then from windows-1251 to utf-8 (assuming that one works in a Unicode environment). After it is decoded, it is desirable to store it in the recoded form instead of the original, in order to be able to read it easily afterwards, and to quote it for replies.
* ↑ i.Scribe / InScribe supports full integration with GNU Aspell, which is its requirement for spell checking.
* ↑ i.Scribe / InScribe requires libjpeg.
* ↑ i.Scribe / InScribe requires libpng.
* ↑ Entourage can link a message to a note.
* ↑ Configurable to start replies at top or bottom, with separate configuration of signature position
* ↑ Thunderbird requires SL8TR extension.
* ↑ Starts replies with cursor at top, but is configurable regarding whether to include a blank space at the top for replies or not; some interleaved-posting users prefer starting the cursor at the top so they can trim the quotes
* ↑ The recoding engine and interface extensions that would solve the described recoding problems have been developed as a patch for Pine; it is to be found in the package pine-4.58L-alt4.src.rpm Archived 2011-08-27 at the Wayback Machine(ftp) for ALTLinux (under the name pine-4.58L-alt2-0.4.1.diff). Its essential feature is to enable to forcibly recode messages, save them in the recoded form, and quote in replies.
* ↑ Pine supports full integration with GNU Aspell or other external speller, which is its requirement for spell checking.

### Database, folders and customization

| Client | Message file format | Encrypted database | Virtual folders | Scheduled backup | New mail notification | New mail notification | New mail notification | New mail notification | Customizable interface | Customizable keybindings | Fragmented messages | Database search with regular expressions support | Indexed search | Search folders | IMAP | IMAP | IMAP | IMAP |
| Client | Message file format | Encrypted database | Virtual folders | Scheduled backup | ticker | tray icon | tooltip | sound | Customizable interface | Customizable keybindings | Fragmented messages | Database search with regular expressions support | Indexed search | Search folders | Search | IDLE |
| Alpine | mbox, mbx, MIX, maildir (with patches), MMDF, tenex, mtx, MH, mx, news, phile | ? | Yes | Partial | ? | ? | ? | Yes | Yes | No | ? | No | Yes | Yes | Yes | No |
| Becky! Internet Mail | mbox | ? | ? | No | Yes | ? | Yes | Yes | ? | ? | ? | Yes | ? | Yes | Yes | Yes |
| Canary Mail | Proprietary | Yes | No | No | ? | Yes | ? | Yes | Yes | Yes | No | No | Yes | Yes | Yes | Yes |
| Citadel | ? | ? | ? | ? | ? | ? | ? | ? | ? | ? | ? | ? | ? | ? | ? | ? |
| Claws Mail | MH, mbox (plugin) | No | No | No | Yes | Yes | Yes | Yes | Yes | Yes | ? | ? | ? | No | Yes | No |
| Courier | Proprietary | Yes (weak) | Yes | ? | ? | ? | ? | ? | Yes (layout) | No | ? | No | No | Yes | No | Yes |
| Elm | ? | ? | ? | ? | ? | ? | ? | ? | ? | ? | ? | ? | ? | ? | ? | ? |
| eM Client | Proprietary (sqlite) | Yes | Yes | Yes | Yes | Yes | No | Yes | Yes | Yes | No | No | Yes | Yes | Yes | Yes |
| EmailTray | Proprietary | Yes | Yes | No | Yes | Yes | No | Yes | No | No | No | No | Yes | Yes | ? | ? |
| Eudora | modified mbox | No | Yes | No | No | Yes | Yes | Yes | Yes | Yes | Yes | Yes | Yes | Yes | Yes | ? |
| Evolution | maildir, mbox, MH | No | Yes | No | No | Yes | Yes | Yes | Partial | Yes | Yes | Yes | Yes | Yes | Yes | Yes |
| Gnus | babyl, maildir, mbox, MMDF, news, rnews, SOUP, outlook, oe-dbx | No | Yes | No | No | ? | ? | ? | Yes | Yes | Yes | Yes | Yes | Yes | Yes | ? |
| GroupWise | Proprietary | Yes | Yes | Yes | ? | Yes | Yes | Yes | Yes | ? | ? | ? | Yes | Yes | Yes | No |
| Hiri | Proprietary | No | No | No | No | No | No | No | Yes | No | No | No | Yes | Yes | No | No |
| IBM Notes | Proprietary | Yes | Yes | Yes | Yes | Yes | Yes | Yes | Yes | Yes | Yes | No | Yes | Yes | ? | No |
| KMail | mbox, maildir | No | Yes | No | ? | ? | ? | ? | Yes | Yes | No | Yes | ? | Yes | Yes | Yes |
| Mailbird | Proprietary | No | Yes | No | Yes | Yes | Yes | Yes | Yes | Yes | No | Yes | Partial | Yes | Yes | Yes |
| Mailpile | ? | ? | ? | ? | ? | ? | ? | ? | ? | ? | ? | ? | ? | ? | ? | ? |
| Microsoft Entourage | Proprietary (Personal Storage Table) | ? | Yes | Partial | ? | ? | ? | ? | Partial | No | No | Partial | Yes | Yes | Yes | Yes |
| Microsoft Office Outlook | Proprietary (Personal Storage Table) | Yes | Yes | Yes | ? | Yes | Yes | Yes | Yes | Yes | ? | ? | Yes | Yes | ? | Yes |
| Mozilla Mail & Newsgroups | mbox | ? | ? | ? | ? | ? | ? | ? | ? | ? | ? | ? | ? | ? | ? | ? |
| Mozilla Thunderbird | mbox, maildir | No | Yes | ? | ? | Yes | Yes | Yes | Yes | ? | No | ? | Yes (as of 3.0) | Yes | Yes | Yes |
| Mulberry | mbox | Partial | Partial | Partial | ? | ? | ? | ? | Yes | ? | ? | Yes | Partial | No | Yes | No |
| Mutt | mbox, MMDF, MH, maildir | Yes (with compressed folders patch) | ? (has limit command) | No | ? | ? | ? | ? | Yes | Yes | ? | Yes | Yes | Yes | Yes | Yes |
| Netscape Messenger | mbox | ? | ? | ? | ? | ? | ? | ? | ? | ? | ? | ? | ? | ? | ? | ? |
| Netscape Messenger 9 | mbox | ? | ? | ? | ? | ? | ? | ? | ? | ? | ? | ? | ? | ? | ? | ? |
| nmh / MH | MH | No | Yes | No | No | ? | ? | ? | Yes | Yes | ? | Yes | Yes | Yes | No | ? |
| Opera Mail | mbox, MH, Proprietary | No | Yes (all folders are virtual) | No | No | Yes | Yes | Yes | Yes | Yes | No | Yes | Yes | Yes | ? | Yes |
| Outlook Express | Proprietary | No | No | No | ? | Yes | No | Yes | No | No | Yes | ? | No | ? | ? | Yes |
| Pegasus Mail | Proprietary (mbox-like) | No | Yes | No | ? | Yes | Yes | Yes | Yes | ? | ? | Yes | ? | Yes | Yes | No |
| Pine | mbox, mbx, MIX, maildir (with patches), MMDF, tenex, mtx, MH, mx, news, phile | ? | ? | ? | ? | ? | ? | ? | ? | ? | ? | ? | ? | ? | ? | No |
| Pocomail | mbox | Yes | Yes | Yes | ? | ? | ? | ? | Yes | ? | ? | Yes | Yes | Yes | ? | ? |
| RoundCube | [IMAP Server] | ? | ? | ? | Yes | No | No | Yes | Yes | Yes | ? | ? | ? | Yes | Yes | ? |
| i.Scribe / InScribe | Proprietary (sqlite) | No | No | No | No | Yes | No | Yes | Yes | No | No | No | No | No | No | Yes |
| SeaMonkey Mail & Newsgroups | mbox | ? | ? | ? | Yes | Yes | Yes | Yes | ? | ? | ? | ? | ? | ? | Yes | Yes |
| SquirrelMail | [IMAP Server] | ? | ? | ? | Yes | No | No | Yes | Yes | Yes | ? | ? | ? | Yes | Yes | ? |
| Sylpheed | MH | No | Yes | No | ? | Yes | ? | ? | Yes | Yes | No | No | No | Yes | ? | No |
| The Bat! | Proprietary | Yes (AES 128 bit) (with Pro and Voyager version) | Yes | Yes | Yes | Yes | No | Yes | Yes | Yes | Yes | Yes (PCRE 6.2) | No | Yes | Yes | Yes |
| Trojitá | IMAP | No | No | No | No | Yes | No | No | Yes | Yes | No | No | Yes | No | Yes | Yes |
| Turnpike | Proprietary | Yes | Yes | ? | ? | ? | ? | ? | ? | ? | Yes | ? | ? | Yes | ? | ? |
| Windows Live Mail | File System (.eml) | No | No | No | No | Yes | ? | Yes | Yes | No | Yes | No | Yes | Yes | ? | ? |
| Windows Mail | ? | ? | ? | ? | ? | ? | ? | Yes | ? | ? | ? | ? | ? | ? | ? | Yes |
| YAM | mbox, maildir, oe-dbx | No | No | No | ? | ? | Yes | Yes | Yes | No | No | No | No | No | No | No |
| Zimbra | File system | No | Yes | Yes | ? | ? | ? | ? | Yes | Yes | Yes | Yes | Yes | Yes | Yes | Yes |
| Client | Message file format | Encrypted database | Virtual folders | Scheduled backup | New mail notification | New mail notification | New mail notification | New mail notification | Customizable interface | Customizable keybindings | Fragmented messages | Database search with regular expressions support | Indexed search | Search folders | IMAP | IMAP | IMAP | IMAP |
| Client | Message file format | Encrypted database | Virtual folders | Scheduled backup | ticker | tray icon | tooltip | sound | Customizable interface | Customizable keybindings | Fragmented messages | Database search with regular expressions support | Indexed search | Search folders | Search | IDLE |
* 1 2 Fragmented messages make it possible, for example, to send a large audio message as several partial messages, and still have it appear to the recipient as a simple audio message rather than as an encapsulated message containing an audio message. RFC 2046
* 1 2 Search Folders are virtual folders that contain views of all email items matching specific search criteria. Search Folders display the results of previously defined search queries.
* ↑ Editable keybindings is part of GNOME, provided "Editable menu accelerators" is enabled in GNOME's "Menus & Toolbars" control applet.
* ↑ Via nnir backends such as Notmuch
* ↑ Fragmented messages are called truncated document in Lotus Notes.
* ↑ With Entourage 2008, you can use AppleScript and various internal/external scheduling mechanisms to create timed backups of Entourage Data.
* ↑ With Entourage 2008 and later versions of 2004, you can use the Spotlight data to search what's in the Entourage database via regular expression in the file system in Terminal or via Spotlight's ...interesting...version of "regular expressions".
* ↑ supported since Office 2007.
* ↑ Thunderbird's interface can be user customized via the use of themes (which can reposition and skin controls)
* ↑ This is for Mulberry's 'offline browsing' capability, which is turned off by default. In the default configuration no local copy of the mail is created.
* 1 2 3 4 Mulberry is a dedicated IMAP client; If the IMAP server has these abilities, Mulberry can use them.
* 1 2 Via Notmuch or other indexers.
* 1 2 Because MH stores each letter in a separate file, it is trivially easy to (externally) search them with grep. This ease is shattered when non-raw encodings are used, such as base64.
* ↑ The Bat! Pro support two methods access to program when database is encrypted: password authorization and token authorization; Voyager support only password authorization and encrypted database is default and only available storage method.

### Templates, scripts and programming languages

| Client | Message templates | Message templates | Message templates | Message templates | Message templates | Message templates | Message templates individual for | Support in message templates scripts, programming languages | Support in message templates scripts, programming languages | Support in message templates scripts, programming languages | Support in message templates scripts, programming languages | Support in message templates scripts, programming languages | Support in message templates scripts, programming languages | Support in message templates scripts, programming languages |
| Client | new | reply | forward | read confirmation | save | print | Message templates individual for | JavaScript | VBScript | PHP Scripts | Python | Regular expressions | Java | Other (specify) |
| Alpine | Yes | Yes | Yes | ? | ? | ? | Any | No | No | No | No | ? | No | ? |
| Becky! Internet Mail | Yes | Yes | Yes | Yes | Yes | Yes | Any account folder | ? | ? | ? | ? | ? | ? |
| Canary Mail | Yes | Yes | Yes | Yes | Yes | Yes | ? | No | No | No | No | No | No | * |
| Citadel | ? | ? | ? | ? | ? | ? | ? | ? | ? | ? | ? | ? | ? | ? |
| Claws Mail | Yes | Yes | Yes | Yes | Yes | Yes | account folder | No | No | No | Yes | ? | ? | Perl |
| Courier | Yes | Yes | Yes | No | Yes | Yes | ? | No | No | No | No | No | No | No |
| Elm | ? | ? | ? | ? | ? | ? | ? | ? | ? | ? | ? | ? | ? | ? |
| eM Client | Yes | Yes | Yes | Yes | Yes | Yes | account | No | No | No | No | No | No | No |
| Eudora | Yes | Yes | Yes | Yes | Yes | Yes | Any | No | No | No | No | Yes | No | No |
| Evolution | Yes | Yes | Yes | Yes | Yes | Yes | ? | ? | ? | ? | ? | ? | ? | ? |
| Gnus | Yes | Yes | Yes | Yes | Yes | Yes | ? | No | No | No | No | Yes | No | elisp |
| GroupWise | Yes | No | No | Yes | Yes | ? | ? | ? | ? | ? | ? | ? | ? | ? |
| Hiri | Yes | Yes | Yes | No | Yes | Yes | Any | No | No | No | No | No | No | No |
| i.Scribe / InScribe | Yes | Yes | Yes | No | No | No | Any | No | No | No | No | No | No | Internal macros (similar to JavaScript) |
| IBM Notes | Yes | Yes | Yes | Yes | ? | ? | ? | Yes | No | No | No | Yes | Yes | LotusScript, Formula language |
| KMail | Yes | Yes | Yes | No | No | No | none | ? | No | No | No | ? | ? | ? |
| Mailpile | ? | ? | ? | ? | ? | ? | ? | ? | ? | ? | ? | ? | ? | ? |
| Microsoft Entourage | Yes | Yes | Yes | Yes | ? | ? | ? | ? | ? | ? | ? | ? | ? | AppleScript, Automator |
| Microsoft Office Outlook | Yes | Yes | Yes | Yes | ? | ? | ? | No | No | ? | No | ? | No | ? |
| Mozilla Mail & Newsgroups | ? | ? | ? | ? | ? | ? | ? | ? | ? | ? | ? | ? | ? | ? |
| Mozilla Thunderbird | Yes | Yes | Yes | Yes | Yes | Yes | profile | Yes | ? | ? | ? | ? | ? | ? |
| Mulberry | Yes | Yes | Yes | Yes | ? | ? | ? | No | No | No | No | ? | ? | ? |
| Mutt | Yes | Yes | Yes | No | ? | ? | Any | No | No | No | No | Yes | ? | Internal macros |
| Netscape Messenger | ? | ? | ? | ? | ? | ? | ? | ? | ? | ? | ? | ? | ? | ? |
| Netscape Messenger 9 | ? | ? | ? | ? | ? | ? | ? | ? | ? | ? | ? | ? | ? | ? |
| nmh / MH | ? | ? | ? | ? | ? | ? | ? | ? | ? | ? | ? | ? | ? | ? |
| Opera Mail | No | No | No | No | No | No | — | No | No | No | No | No | No | No |
| Outlook Express | Yes | Yes | ? | Yes | ? | ? | ? | Yes | Yes | ? | ? | ? | ? | ? |
| Pegasus Mail | Yes | Yes | Yes | Yes | ? | ? | ? | ? | ? | ? | ? | ? | ? | ? |
| Pine | Yes | Yes | Yes | ? | ? | ? | Any | ? | No | No | ? | ? | No | ? |
| Pocomail | Yes | Yes | Yes | ? | ? | Yes | ? | No | No | No | No | No | No | PocoScript |
| RoundCube | Yes | Yes | Yes | Yes | Yes | Yes | Yes | No | No | No | No | No | No | ? |
| SeaMonkey Mail & Newsgroups | ? | ? | ? | ? | ? | ? | ? | ? | ? | ? | ? | ? | ? | ? |
| SquirrelMail | Yes | Yes | Yes | Yes | Yes | Yes | Yes | No | No | No | No | No | No | ? |
| Sylpheed | Yes | Yes | Yes | ? | ? | ? | ? | No | No | No | No | No | ? | ? |
| The Bat! | Yes | Yes | Yes | Yes | Yes | Yes | account folder address book group contact | Yes | Yes | Yes | Yes | Yes | PCRE 6.2 | Internal and plugins macros |
| Turnpike | ? | ? | ? | ? | ? | ? | ? | ? | ? | ? | ? | ? | ? | ? |
| Windows Live Mail | Yes | Yes | ? | Yes | ? | ? | ? | Yes | No | ? | ? | ? | ? | ? |
| Windows Mail | ? | ? | ? | ? | ? | ? | ? | ? | ? | ? | ? | ? | ? | ? |
| YAM | Yes | Yes | Yes | ? | Yes | Yes | ? | No | No | No | No | ? | ? | ARexx |
| Zimbra | Yes | Yes | Yes | Yes | Yes | Yes | Any | No | No | No | No | No | ? | ? |
| Client | Message templates | Message templates | Message templates | Message templates | Message templates | Message templates | Message templates individual for | Support in message templates scripts, programming languages | Support in message templates scripts, programming languages | Support in message templates scripts, programming languages | Support in message templates scripts, programming languages | Support in message templates scripts, programming languages | Support in message templates scripts, programming languages | Support in message templates scripts, programming languages |
| Client | new | reply | forward | read confirmation | save | print | Message templates individual for | JavaScript | VBScript | PHP Scripts | Python | Regular expressions | Java | Other (specify) |
* 1 2 Thunderbird supports HTML templates with "Stationery" add-on.
* ↑ The Bat! supports JavaScript in message templates with the JavaScript Macro plugin.
* ↑ The Bat! supports VBScript in message templates with the XMP plugin.
* ↑ The Bat! supports PHP in message templates with the XMP plugin.
* ↑ The Bat! supports Python in message templates with the TBPyxie plugin.
* 1 2 3 Weak "stationery" system that only accept pages done with Word.

## Internationalization

The Bat! supports Email Address Internationalization (EAI).
As of October 2016, email clients supporting SMTPUTF8 included Outlook 2016, mail for iOS, and mail for Android.