Todd Vierling wrote this in response to my post on the captioned topic,
V> Are you sure this isn't the mailing list manager at work? Typically _they_
V> change the envelope sender such that bounces won't loop.
Dead-on 100% positive, as there is no mailing list manager. The list runs
under my own homebrew procmail recipes (without SmartList). Moreover, it
has [for historical reasons] two submission addresses and an owner- alias
for only one of them. Envelopes are not clobbered on mail to the other
submission address, and for the one whose envelopes are rewritten, changes
to the expansion of the owner- alias change the results of the clobbering.
T> Since newer sendmail versions do not add Return-Path: any more, the original
T> envelope sender information is lost.
V> Huh? Sendmail 8.9.0 (and now 8.9.1) adds a Return-Path: here. And I have
V> several owner- addresses.
I'm not a system administrator, but as a user I've seen three installations
of recent sendmails, and zero of the three add Return-Path:. If Todd says
it can be done, I believe him, so when the sysadmin of my list host returns
to town Monday I'll ask her to try that first.