I have been using Ability mail server for about 2 years, and right now no email is going through and all messages are being returned with this message attached. Any help would be greatly appreciated.
In the last 24 hours we have received a collection of emails informing us that one of the RBLs have gone down, and some users have experienced this issue. What I recommend you do is that you access the SPAM Filtering RBL settings and remove SPEWS and SORBS from the list.