Added option include_sender_header to suppress rewrite of the Sender header which confuses Outlook (formerly known as FAQ 2.3). See also <http://mail.python.org/pipermail/mailman-developers/2006-July/019040.html>. Bug #266824.

5 files changed, 51 insertions, 2 deletions

diff --git a/Mailman/Defaults.py.in b/Mailman/Defaults.py.in
index db75971d..e1ede271 100644
--- a/Mailman/Defaults.py.in
+++ b/Mailman/Defaults.py.in
@@ -1040,6 +1040,14 @@ DEFAULT_OBSCURE_ADDRESSES = Yes
 # lists with no archives).
 ALLOW_RFC2369_OVERRIDES = Yes
 
+# RFC 2822 suggests that not adding a Sender header when Mailman is the agent
+# responsible for the actual transmission is a breach of the RFC.  However,
+# some MUAs (notably Outlook) tend to display the Sender header instead of the
+# From details, confusing users and actually losing the original sender when
+# forwarding mail.  By setting this variable to Yes, list owners will be
+# given the option to avoid setting this header.
+ALLOW_SENDER_OVERRIDES = Yes
+
 # Defaults for content filtering on mailing lists.  DEFAULT_FILTER_CONTENT is
 # a flag which if set to true, turns on content filtering.
 DEFAULT_FILTER_CONTENT = No
diff --git a/Mailman/Gui/General.py b/Mailman/Gui/General.py
index 8271a30e..21547cb8 100644
--- a/Mailman/Gui/General.py
+++ b/Mailman/Gui/General.py
@@ -414,6 +414,29 @@ class General(GUIBase):
              does not affect the inclusion of the other <tt>List-*:</tt>
              headers.)"""))
             )
+        # Suppression of Sender header modification
+        if mm_cfg.ALLOW_SENDER_OVERRIDES:
+            rtn.append(
+                ('include_sender_header', mm_cfg.Radio,
+                 (_('No'), _('Yes')), 0,
+                 _("""Should the <tt>Sender</tt> header be rewritten for this
+                 mailing list to avoid stray bounces?  <em>Yes</em> is
+                 recommended."""),
+
+                 _(""""<a href="http://www.faqs.org/rfcs/rfc2822.html">RFC
+                 2822</a> defines the <tt>Sender</tt> header and defines it
+                 as "the mailbox of the agent responsible for the actual
+                 transmission of the message."  Mailman replaces this header
+                 per default with the list's bounce address.
+                 
+                 <p>While it is debatable if Mailman is such an agent, setting
+                 this header helps directing bounces from some broken MTAs to
+                 the right destination.  On the other hand do some mail
+                 readers show unexpected behaviour if this header is set (like
+                 missing addresses in forwarded mails and copies sent to the
+                 bounce address on reply-to-all), so it can be disabled 
+                 here."""))
+                )
 
         # Discard held messages after this number of days
         rtn.append(
diff --git a/Mailman/Handlers/SMTPDirect.py b/Mailman/Handlers/SMTPDirect.py
index 8e3c7d73..1930a549 100644
--- a/Mailman/Handlers/SMTPDirect.py
+++ b/Mailman/Handlers/SMTPDirect.py
@@ -355,10 +355,26 @@ def bulkdeliver(mlist, msg, msgdata, envsender, failures, conn):
     # 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']
+    #
+    # With some MUAs (eg. Outlook 2003) rewriting the Sender header with our
+    # envelope sender causes more problems than it solves, because some will 
+    # include the Sender address in a reply-to-all, which is not only 
+    # confusing to subscribers, but can actually disable/unsubscribe them from
+    # lists, depending on how often they accidentally reply to it.  Also, when
+    # forwarding mail inline, the sender is replaced with the string "Full 
+    # Name (on behalf bounce@addr.ess)", essentially losing the original
+    # sender address.
+    # 
+    # The drawback of not touching the Sender: header is that some MTAs might
+    # still send bounces to it, so by not trapping it, we can miss bounces.
+    # (Or worse, MTAs might send bounces to the From: address if they can't
+    # find a Sender: header.)  So instead of completely disabling the sender
+    # rewriting, we offer an option to disable it.
     del msg['errors-to']
-    msg['Sender'] = envsender
     msg['Errors-To'] = envsender
+    if mlist.include_sender_header:
+        del msg['sender']
+        msg['Sender'] = envsender
     # Get the plain, flattened text of the message, sans unixfrom
     # using our as_string() method to not mangle From_ and not fold
     # sub-part headers possibly breaking signatures.
diff --git a/Mailman/MailList.py b/Mailman/MailList.py
index 6083fb12..45ce6f09 100644
--- a/Mailman/MailList.py
+++ b/Mailman/MailList.py
@@ -363,6 +363,7 @@ class MailList(HTMLFormatter, Deliverer, ListAdmin,
         self.available_languages = []
         self.include_rfc2369_headers = 1
         self.include_list_post_header = 1
+        self.include_sender_header = 1
         self.filter_mime_types = mm_cfg.DEFAULT_FILTER_MIME_TYPES
         self.pass_mime_types = mm_cfg.DEFAULT_PASS_MIME_TYPES
         self.filter_filename_extensions = \
diff --git a/Mailman/versions.py b/Mailman/versions.py
index 81fafd5a..031094ed 100644
--- a/Mailman/versions.py
+++ b/Mailman/versions.py
@@ -353,6 +353,7 @@ def NewVars(l):
     add_only_if_missing('send_goodbye_msg', mm_cfg.DEFAULT_SEND_GOODBYE_MSG)
     add_only_if_missing('include_rfc2369_headers', 1)
     add_only_if_missing('include_list_post_header', 1)
+    add_only_if_missing('include_sender_header', 1)
     add_only_if_missing('bounce_score_threshold',
                         mm_cfg.DEFAULT_BOUNCE_SCORE_THRESHOLD)
     add_only_if_missing('bounce_info_stale_after',