libsmtp enables developers to send mail directly via SMTP from a program. It is designed to be flexible, easy to use and have a small code size (embedded linux) and is licensed under the LGPL, so it can be included within closed sourced applications, too. libsmtp has been tested under Linux and NetBSD, but should compile on all recent Unixes and maybe even Windows. It can send mail to multiple recipients in one go, and supports sending to CC and BCC recipients too. The development version has (wobbly) support for attachments (this being multiple body parts), different character sets and transport encodings.