iSync - iSync is a software application published by Apple Inc.
imapsync - Console-based utility for migrating IMAP mailboxes.
MailStore - MailStore Home - A 100% free single-private-user desktop solution
Fetchmail - The Fetchmail Project
OfflineIMAP - OfflineImap synchronizes email between an IMAP server and a MailDir or between two IMAP servers.
getmail - Official website for getmail version 5, an extensible mail-retrieval program with support for POP3, IMAP, SDPS, SSL, domain mailboxes, message filtering, and other features.