Mail rule/smart folder help

I am trying to create a rule or smart folder in either Mail or Outlook (either Windows or Mac) that will filter email in which somebody outside my company is in the To: or Cc: field. The tricky part is that most of the messages also have people inside my company in either or both of those fields, too. So a rule or folder with “does not contain” filters out too much.

Anyone have an idea I should try?

I think you’re out of luck with macOS Mail. You want to identify mail that has been sent or copied to someone outside your company (call it, which mean you’ll a rule along the lines of

TO: (or CC:) “contains” NOT

As you rightly say, that different from “does not contain”, which will only work if the external address is the sole addressee.

From the fact that you mentioned Outlook, I guess that your company may be a Microsoft house, in which case it’s probably using Microsoft Exchange as the mail server. The server will know which traffic its directing to external domains and can apply processing rules to it using “mail flow rules” (also called “transport rules” (see, so perhaps your company’s IT people could help.

Thanks for the input, David. We’ve migrated to Outlook 365, so I’m not sure we even have our own Exchange server anymore. I’ll have to look into it.