[Mailman-Users] Sender field

Neal Groothuis ngroot at imsa.edu
Fri Apr 28 18:02:11 CEST 2006

It does not appear that Mailman modifies the "Sender:" field to comply 
with RFC 2822.  The list-bounces address is not the mailbox of the agent 
responsible for transmitting the message, as required in section 3.6.2. 
  The mailbox of the agent responsible for the transmission of the 
message would be the list-owner address.

Mailman's use the "Sender:" field does not seem to be in line with the 
intent of the RFC, nor with current usage of the field.   The example 
given in the RFC is of a secretary sending an email on behalf of someone 
else.  Outlook obviously interprets it this way.  Some versions of 
Thunderbird display both the Sender: and From: lines to the user, which 
may prove confusing if the Sender: address is not a person or an obvious 
alias for one.  Gmail uses it if you choose a "From" address that is not 
your gmail.com address.

Further, if Mailman is going to change the "Sender:" field, it should 
add Resent-* headers, per section 3.6.6 of RFC 2822; otherwise, the 
original sender information is lost.  The RFC does say that this is to 
be used when "users" reintroduce a message into the system, further 
providing evidence that automated components of the mail routing system 
shouldn't be changing these.  (Note that MTAs don't change the Sender: 
field, despite being, by their nature, agents responsible for 
transmission of messages.)

RFC 2369 provides headers which are to be used by mail list software to 
identify the various ways of interacting with the list, and Mailman 
already adds them.  This makes adding this information to the Sender: 
field redundant.

Based on all of this, Mark's note that there are some MTAs which bounce 
to the Sender: address is the only reason that I've seen why this 
behavior should continue.  Does anyone know what MTAs these are, or if 
they're even still in use?  If these buggy MTAs are common, I would 
suggest that an option be added to the list to enable this behavior, 
marked as an accomodation for buggy MTAs, and defaulting to "off".  I'll 
see if I can scrounge up the time to submit a patch to accomplish this, 
if it'll actually get included in a future release; otherwise I won't 
waste my time.  If these MTAs are not in use, I stand by my original 
recommendation to comment out/remove the two lines responsible for the 

At any rate, the "keep patching" suggestion is unhelpful.   This is 
obviously a problem that many people are running into, enough that 
there's a FAQ entry about it.  It should be addressed.

More information about the Mailman-Users mailing list