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).
And where I can disable user?
In Edit Mail and FTP Users I can only see Delete Selected Users bottom.
Well, he’s suggesting to disable the “Mailbox for the user”, rather than the user itself.
To do that, go into Edit Mail and FTP users, choose the user in question, and choose Email settings.
I believe you can disable the Mailbox by setting "Primary email address enabled" to "No".
Before trying any of this, I’d make certain you have a backup of the Virtual Server (though, hopefully you’re doing that at least daily anyhow