An IMAP e-mail client for X-windows. It has support for using many servers at once and IMAP over SSL. (C++) [GNU/Linux]

Mail attachments from the commandline. (Shell script) [GNU/Linux, Unix]

A mail retrieval and forwarding utility intended to be used over on-demand TCP/IP links (such as SLIP or PPP connections). [GNU/lInux, Unix]

Checks for mail within a file, a qmail or MH style dir, or an IMAP4 or a POP3 server. (C) [GNU/Linux, Unix]

A POP3 mail retriever with reliable qmail-style Maildir and mbox delivery, and domain (multidrop) mailbox support. (Python) [GNU/Linux, Unix]

A mail filter/local delivery agent with a perl-ish filtering language and maildir support. (C++) [GNU/Linux, Unix]

A utility to get rid of unwanted spam mails, before downloading them from the POP3 mailbox. (C++) [GNU/Linux, Unix, Windows 9x/2000/NT]

Synchronizes a collection of mailboxes, which may be on the local filesystem or on an IMAP server. (C++) [OS Independent]

A WindowMaker dock app that monitors a POP3 mailbox to inform you when mail arrives. It can be configured via a GTK+ GUI. (C) [GNU/Linux]