To reopen an old discussion: I would like to request that a feature be added in the next version of Mailman to allow a list administrator to disable rewriting of the "Sender:" header, or (better) for this behavior to be eliminated from Mailman altogether. Rationale: - Outlook treats the Sender field as a person sending on behalf of another. This seems to me to be a reasonable interpretation of the Sender field, per RFC 2822 3.6.2. When a "bounces" address is included in the sender field, Outlook displays something along the lines of "From listname-bounces+jim=reader.domain.com@mailman.server.com On behalf of fred@poster.domain.com". (See Mailman FAQ entry 2.3). This is undesirable. - Thunderbird also displays the sender field, which presents similar confusion. - Useful information (the original content of the Sender: header) is lost by doing this. - Bounces go to the envelope sender or Return-Path: header, not the Sender: header, so this is not necessary for proper bounce handling. - Again from RFC 2822 3.6.2, the Sender: header should contain the address of the agent responsible for transmitting the message, meaning that a person who sends mail to the address in that header should expect to reach said agent, not suggest to Mailman that a message bounced. - Information regarding interacting with the list is provided by the List-* headers; including it in the Sender: field is unnecessary. Removing this (IMO) unwanted functionality is trivial: diff -ru mailman-2.1.5.orig/Mailman/Handlers/SMTPDirect.py mailman-2.1.5/Mailman /Handlers/SMTPDirect.py --- mailman-2.1.5.orig/Mailman/Handlers/SMTPDirect.py 2004-01-22 17:02:07.0000 00000 -0600 +++ mailman-2.1.5/Mailman/Handlers/SMTPDirect.py 2006-04-26 13:48:45.0000 00000 -0500 @@ -348,9 +348,9 @@ # the Sender header at all. Brad Knowles points out that MTAs tend to # wipe existing Return-Path headers, and old MTAs may still honor # Errors-To while new ones will at worst ignore the header. - del msg['sender'] + # del msg['sender'] del msg['errors-to'] - msg['Sender'] = envsender + # msg['Sender'] = envsender msg['Errors-To'] = envsender # Get the plain, flattened text of the message, sans unixfrom msgtext = msg.as_string()