- Plesk for Linux
How to migrate mail content from 3rd party mail service to Plesk?
Plesk does not provide such functionality yet. Take part in product improvement by voting for existing feature on Plesk Uservoice.
For manually content migration use rsync-imap or another 3rd party tool. Before mail content migration create the domain and all mail accounts on Plesk server.
Warning: Such functionality was not tested in Plesk and would be performed on your side and at your own risk.