Email services use communication protocols:
POP: Post Office Protocol (recommended)
Provides the ability to transfer incoming email from the server into your email application inbox. Normally your email application would subsequently delete this transferred email from the server, although maybe not immediately.
IMAP: Internet Message Access Protocol
This allows email to be stored on the server and for an email application to access it, including keeping a full or partial copy of the emails within the email application. Email changes are synchronised: changing emails within the email application will reproduce those changes on the server, changing emails on the server will reproduce those changes in the email application.
Note: When using IMAP, most email applications will not synchronise the outbox or sent items folders. Those folders are local/private to the email application.
SMTP: Simple Mail Transfer Protocol
This allows you to send outgoing email. Normally both POP and IMAP will also use SMTP.
Whilst Arrow Technology allows all of these protocols, we do not provide large server mailboxes for use with IMAP. If you require a large server mailbox then we recommend using an email service such as Gmail or Office 365.