When you delete an email (from your Trash folder!), there is no artificial delay between when you click delete and when that message is actually deleted from StartMail servers. It’s practically instant, so there’s no need to worry about StartMail retaining anything you don’t want to be preserved on the Net anymore.
It will, however, remain on our backup servers for three days. That’s the length of time that each backup snapshot is held, and backups are an essential feature for any email service. The backups are buried deep inside private networks, protected by many layers of security.
The backups contain your closed vault, so your password would be required to open it. As a consequence, neither StartMail nor an attacker would be able to access your emails within a backup.
After the three-day period has elapsed, the previous backup is erased forever.