Bug? Notifications with user as sender

[Peter Ostry]

Nothing about that in the Bug tracker for 3.7
Strange thing, I have now 6 emails of this kind. Not really bad but irritating and the users cannot reply (yes, they should not, but sometimes they do). We send notification emails to a mailing list.

Example:
Username = ThisUser
Email Address = hismail@addre.ss
("ThisUser" opened a new thread in the forum)

But I get the notification from ThisUser@smtp-in.ostry.com where the part after the @ is our incoming mailserver.
Another person gets the mail from ThisUser@redmatica.com which shows his incoming mailserver.

I checked the user profiles and the sender address is definitely the username while the email address gets ignored.