We have a mail server (SMTP, IMAP , spam assassin , ClamAV ) running on Ubuntu and there are more than 200 mail accounts. We are looking for a backup solution for mail, which will allow us to take the backup of individual accounts, as per our backup policy. The situation is that around 25 of the accounts need frequent backups while the rest are not that important.
So can anyone suggest a good solution, preferably open source. If it has a GUI interface it would be preferred.