A client of ours attempted a mail migration from another ISP to one of our smartermail 17 servers (Build 7118 ) and reported that the inbox did not migrate.
We then attempted the migration and thought that the client may have used the "Smartermail" option as the source server as the loosing ISP runs smartermail version 5, so we opted for a "Other" mail migration.
First attempt to pop the mail failed with "username and password" error, despite the password being 100% correct. Changing the drop down to imap (without changing password) connected.
30 minutes later, no emails.
I then fired up my trusty imapsync, and after a few minutes it failed with issues on the targer server (smartermail Build 7118).
Edited my imapsync script to sync the mails to a legacy smartermail server that we have (version 15) and the sync runs, and is running without issue.