Dovecot Quotas: Now Counting Reality Instead of Imagination

Turns out some users were right. Dovecot was counting imaginary gigabytes.

For years, a few people noticed something that didn’t make sense. They would hit their quota limit, get “mailbox full” errors, and check their disk usage only to find plenty of room left. Most users never ran into it, but those who did were understandably confused.

The reason came down to how Dovecot measures mailbox size. By default, it doesn’t look at what’s actually stored on disk. It looks at the declared message size, meaning the size reported when the email was sent. That number is usually larger than the space the message ends up taking on disk, because attachments are base64-encoded during transmission, which inflates their size.

So, Dovecot thought some mailboxes were full even when they weren’t.

We fixed it.

Dovecot now measures quota based on real disk usage. What you see in DirectAdmin now matches what’s actually on the server. For most users, nothing will change. For those who hit quota limits when they shouldn’t have, this brings things back to reality.

If your mailbox suddenly feels like it got bigger, it didn’t. It was always that size. Dovecot just stopped lying about it.