[Mailman-Users] corporate spam filter operation

[Matt Morgan]

This question is a little off-topic.

Are there corporate, enterprise spam-killing services that work on a
user-by-user basis, rather than a message-by-message basis? For example,
where the same message, sent to a few different people, might be rejected as
spam for one recipient but not others?

I'm seeing failures in patterns I didn't expect. We often have many members
in the same domain. I thought I'd see that every message to a domain was
rejected (because it was judged to be spam), or that most of them would
succeed (because it's not judged to be spam, but maybe we have a few old/bad
addresses).

What I'm seeing is that often, about 50% of the messages to a domain are
rejected. It seems like too many for them all to just be bad, old addresses
(although that's possible--this list has not been updated for a while), but
too few for them to have been rejected by spam filters.

I'm delivering messages individually, in case that matters.

Any thoughts/opinions?

Thanks a lot,
Matt