What are some alternatives?
When comparing iSync and MailStore, you can also consider the following products
OfflineIMAP - OfflineImap synchronizes email between an IMAP server and a MailDir or between two IMAP servers.
Gmvault - Backup the emails in your Gmail account.
imapsync - Console-based utility for migrating IMAP mailboxes.
Piler - Piler is an open source email archiving solution with all the necessary features for your enterprise
MigrationWiz - MigrationWiz provides on-demand mailbox migration services through a fully automated cloud-based...
Mail Backup X - Your one stop mail backup and archiving tool for Mac.