We use Message Labs for anti-spam prevention service. They are pretty good at stopping most of the spam, but not all.
For those of you who are not familiar, we point our MX records to Message Labs servers that they specify. Then Message Labs SMTP servers filter out spam and viruses using their own algorithms and forward on the good messages to our inbound SMTP gateway.
The problem is that Message Labs can’t block backscatter as they would block valid non delivery failures in the process.
How are you coping??
