In System Settings -> Server Templates -> Default Settings -> Mail for domain I got option "Format for usernames that include domain" to change to ex. username@domain, but if I got already created Virtual Server and I would like to change that format from username.domain to username@domain, how can I do that?
I think you can just disable and re-enable the mailbox for that user. But, I would test first to be sure it doesn’t do anything nasty (like delete mail preferences…I’m pretty much certain it won’t delete the mail itself, but it might lost other stuff).