I'm using mailman-1.0b10 + exim-2.10.

Mar 30 13:10:08 nbeckerpc Mailman mail-wrapper: Failure to exec script. WANTED gid 12, GOT gid 99. (Reconfigure to take 99?)

I can reconfigure mailman or exim to set the gid, but why is it needed at all? Since wrapper is sgid, why does it care what gid was used to invoke it? Just additional security check?