What are some alternatives?
When comparing mnIMAPSync and Mail Backup X, you can also consider the following products
imapsync - Console-based utility for migrating IMAP mailboxes.
MailStore - MailStore Home - A 100% free single-private-user desktop solution
Yippie Move - The world's best email transfer tool
Piler - Piler is an open source email archiving solution with all the necessary features for your enterprise
OfflineIMAP - OfflineImap synchronizes email between an IMAP server and a MailDir or between two IMAP servers.
Gmvault - Backup the emails in your Gmail account.