Considering that a distribution list and mail group are the same, can you send to an Outlook mail group but exclude either other groups in the mail group or individuals (in the sense of set difference: a\b)?
For example, you have a mail group X, and X contains, among other mail recipients, y - can you send to X but excluding y?
(Of course, you could list, say, a group of 500 and search and exclude, say, 10 of them, but is there a better way?)