sendmail 4.0 without -f picks return path user at random

[Benson Margulies]

We are running 4.0.1. We are using really minimally adjusted sendmail.cf
files. We observe the following entertaining phenomena:

when mail is sent from one person to another (locally), the return path is
set to some user OTHER than the sender. The mapping from sender to return
path is consistent for any given person, but varies from person to person.
I've checked, and there are no duplicated uid's or any such bizarrity.

Has anyone else seen this? 


-- 
Benson I. Margulies