I am a new user to OTRS (2.4.7 running on Ubuntu Server), and I have hit a snag.
Mail seem to work, Notification goes out, incomin gtickets are pulled by Postmaster into my queue.
When I open a ticket, I see that it was sent by "firstname.lastname@domain.com", just as I expect.

But, I cannot reply to a ticket, there is no Email-address listed by Compose Answer (email):  

What may I been missing here? I have gone over the manual this weekend, as well as a bit of Google'ing, but no luck.