/var/log/web.log

Sometimes, I had backuped Maildir because I would update the server... Often, I was too lazy to reimport the mails into the new Maildir...

But it's not that complicated! At least this approach works:

# doveadm import -u triaxx -U triaxx maildir:/home/triaxx/mail.bak backup all

The mail.bak directory is a Maildir structure with the cur, new and tmp subdirectories. It will create a .backup.INBOX subdirectory in which the mails will have been copied.