Aha, the problem was a different one from what I thought.

It wasn't the "To"s that were the problem.

The problem was that one of the "From" addresses in the list is both a return address from a spam server, and it's also a group list, and so any joeuser member of that group list counts as being from that group list, and thus gets included in the filter.

In other words, we get messages from the build server with a return address of "[email protected]". But there is also a group list, named "mycompany build mail" with the same return address "[email protected]" and which has dozens of members.

I want to spambin messages from the build server, but not spambin messages from that group list.

Should be easy, right? I just make sure that, in outlook, when creating the rule, I make sure the filter is for "[email protected]" instead of the group list "mycompany build mail". Right?

Doesn't work. No matter how carefully I type it into Outlook or OWA, it always always always converts it to the group list. I can't NOT convert it into a group list when I enter it. Sigh.