Claus Assmann <ca@informatik.uni-kiel.de>
Andy Mitchell <afm@biotech.ufl.edu>
Subir Grewal <subir@indiaserver.com>
padaki@mach5.tamu.edu (Padmanabh M Padaki)
"Karl E. Vogel" <vogelke@c17.wpafb.af.mil>
The original problem was that people receiving email from some of our users were
getting incomplete return addresses (no domain name), so using the reply feature
of their mailers resulted in bounced messages.
It turned out that some of the receiving systems (IBM mainframes mostly) were
taking the return address from the SMTP negotiation session rather than from the
message header. I presume this was done because the negotiation verifies that the
sender listed there is a legitimate user on the sending system and prevents mail
from being received with bogus return addresses.
The problem was that our mail is forwarded to our mail server machine which then
forwards it to the next system outside our domain. Ruleset 11 forms the sender
name for forwarding to the mail server and since the server is local to our
domain, no domain name was added to the sender name.
Note that this is done in ruleset 11 on our version of sendmail (Solaris 2.5
distribution) but appeared to be in ruleset 12 on other versions. YMMV.
That sender name is forwarded to the receiving system which verifies that the
sender name is legitimate with our mail server. This works properly without the
domain name attached.
Some receiving systems would then use this domainless sender name in the "From:"
field. Replies would, of course, bounce because the address would have no domain
name attached.
Modifying ruleset 11 to include the domain fixed the problem.
Thanks again to all who helped.
Rick