I've just set up a new mail server (Dovecot/Postfix, IMAP only) and I'm trying to migrate all the messages from the old server to the new one. The server handles mail for a small company with half-a-dozen accounts. The problem is that I can't actually find a lot of the older messages on the server.
If I create a new install of Thunderbird, and connect to the old server to see my own account, I can see messages going back many years (to 2000). However, when I actually try to find these messages, the Maildir in my home directory only goes back to 2016. There are several other old Maildir directories which go back to 2000, which were initially copied from old servers as they were decommissioned. However, these directories are in arbitrary backup locations and are not referenced during any login to Dovecot.
So how can Thunderbird see these messages? Presumably dovecot has a way to point to different Maildirs as required?
And do I actually need to know any of this to copy over all the old emails? I've found imapsync, which seems to require only a login, so might find everything anyway.
