Migrating from non-toaster qmail
From QMail-Toaster
Here is one way to upgrade from an older version (or non-Toaster version) that is using vpopmail and mysql support:
(copy and pasted from the mailing list)
If the old server is using vpopmail with mysql support then the backup/restore script should work. If you download it and look at it, you'll see that backs up the mysql database, the vpopmail dir and your control files. The restore portion put the database back (vpopmail - you may need to edit your vpopmail.mysql file or change the DB name after you restore it) and the vpopmail dir, then restores the permissions and fixes and queue issues that may have been copied over. The backup/restore script moves everything; it doesn't break the domains into parts, but this can be worked around as well. Restore the entire shebang on the new machine, and change the DNS entries for the domain you want to move. Make sure to delete the domain from the old machine and set it up as a caching machine. Once you're ready to move the next domain, change the DNS, and then rsync the old machine's vpopmail dir for that domain so the emails all get moved. Then delete the domain from the old machine and set it up as a caching server. Continue until you get it all moved. I would suggest at least testing to make sure the data gets moved before you actually undertake this.