K-9 Mail – Advanced Email for Android
Read/sync your IMAP mailboxes [Python]
http://imapfw.offlineimap.org IMAP/mail framework under MIT licence and written in Python
Mail App with integrated OpenPGP encryption
Check mail when it matters in the clouds.
C++ Mail manager
Forward mail from gmail IMAP to a callback URL, simply.
Program to securely send and receive HTML e-mails (and of course normal text e-mails too)