Why not set up an email account or 2 on the server?
I did just that. And you know what happened? After I had gone through all the setting up and the adjustments on the server and my email client I changed in the ACP of the forum the mail type from SMTP to PHP. And then...SMTP with the Gmail account started working again, but not the PHP sendmail.

Looks like the mod installations a few weeks ago must have caused this bug.
Sorry to all who didn't get their activation mail and PM notifications in time.