What are some alternatives?
When comparing MailStore and Gmvault, you can also consider the following products
Piler - Piler is an open source email archiving solution with all the necessary features for your enterprise
Mail Backup X - Your one stop mail backup and archiving tool for Mac.
imapsync - Console-based utility for migrating IMAP mailboxes.
MozBackup - Backup tool for Firefox and Thunderbird
MailSteward - MailSteward : The Ultimate E-mail Manager for Mac OS X
Got Your Back - Got Your Back (GYB) is a command line tool that backs up and restores your Gmail account.