What are some alternatives?
When comparing imapsync 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.
iSync - iSync is a software application published by Apple Inc.
Piler - Piler is an open source email archiving solution with all the necessary features for your enterprise
Yippie Move - The world's best email transfer tool
Mail Backup X - Your one stop mail backup and archiving tool for Mac.