[You Need a Thneed]

At work, we hosted our own mail server for several years. At some point, I think some kind of forwarding was allowed (accidentally I think), which seems to have put our domain on some kind of a banned list. For most people, our email works, however, there are specific people, that, for some reason, cannot SEND email to us - it always bounces back to them. I believe that we can send out to anyone.

In the last year, we have switched our email to be controlled by Gmail - still using our old mail domain. The problem still remains.

Any ideas what might of caused this? And more specifically, is there anything we can do to fix the problem?