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diff --git a/src/mailman/Bouncers/DSN.py b/src/mailman/Bouncers/DSN.py
new file mode 100644
index 000000000..37e5bcb83
--- /dev/null
+++ b/src/mailman/Bouncers/DSN.py
@@ -0,0 +1,99 @@
+# Copyright (C) 1998-2009 by the Free Software Foundation, Inc.
+#
+# This file is part of GNU Mailman.
+#
+# GNU Mailman is free software: you can redistribute it and/or modify it under
+# the terms of the GNU General Public License as published by the Free
+# Software Foundation, either version 3 of the License, or (at your option)
+# any later version.
+#
+# GNU Mailman is distributed in the hope that it will be useful, but WITHOUT
+# ANY WARRANTY; without even the implied warranty of MERCHANTABILITY or
+# FITNESS FOR A PARTICULAR PURPOSE.  See the GNU General Public License for
+# more details.
+#
+# You should have received a copy of the GNU General Public License along with
+# GNU Mailman.  If not, see <http://www.gnu.org/licenses/>.
+
+"""Parse RFC 3464 (i.e. DSN) bounce formats.
+
+RFC 3464 obsoletes 1894 which was the old DSN standard.  This module has not
+been audited for differences between the two.
+"""
+
+from email.Iterators import typed_subpart_iterator
+from email.Utils import parseaddr
+
+from mailman.Bouncers.BouncerAPI import Stop
+
+
+
+def check(msg):
+    # Iterate over each message/delivery-status subpart
+    addrs = []
+    for part in typed_subpart_iterator(msg, 'message', 'delivery-status'):
+        if not part.is_multipart():
+            # Huh?
+            continue
+        # Each message/delivery-status contains a list of Message objects
+        # which are the header blocks.  Iterate over those too.
+        for msgblock in part.get_payload():
+            # We try to dig out the Original-Recipient (which is optional) and
+            # Final-Recipient (which is mandatory, but may not exactly match
+            # an address on our list).  Some MTA's also use X-Actual-Recipient
+            # as a synonym for Original-Recipient, but some apparently use
+            # that for other purposes :(
+            #
+            # Also grok out Action so we can do something with that too.
+            action = msgblock.get('action', '').lower()
+            # Some MTAs have been observed that put comments on the action.
+            if action.startswith('delayed'):
+                return Stop
+            if not action.startswith('fail'):
+                # Some non-permanent failure, so ignore this block
+                continue
+            params = []
+            foundp = False
+            for header in ('original-recipient', 'final-recipient'):
+                for k, v in msgblock.get_params([], header):
+                    if k.lower() == 'rfc822':
+                        foundp = True
+                    else:
+                        params.append(k)
+                if foundp:
+                    # Note that params should already be unquoted.
+                    addrs.extend(params)
+                    break
+                else:
+                    # MAS: This is a kludge, but SMTP-GATEWAY01.intra.home.dk
+                    # has a final-recipient with an angle-addr and no
+                    # address-type parameter at all. Non-compliant, but ...
+                    for param in params:
+                        if param.startswith('<') and param.endswith('>'):
+                            addrs.append(param[1:-1])
+    # Uniquify
+    rtnaddrs = {}
+    for a in addrs:
+        if a is not None:
+            realname, a = parseaddr(a)
+            rtnaddrs[a] = True
+    return rtnaddrs.keys()
+
+
+
+def process(msg):
+    # A DSN has been seen wrapped with a "legal disclaimer" by an outgoing MTA
+    # in a multipart/mixed outer part.
+    if msg.is_multipart() and msg.get_content_subtype() == 'mixed':
+        msg = msg.get_payload()[0]
+    # The above will suffice if the original message 'parts' were wrapped with
+    # the disclaimer added, but the original DSN can be wrapped as a
+    # message/rfc822 part.  We need to test that too.
+    if msg.is_multipart() and msg.get_content_type() == 'message/rfc822':
+        msg = msg.get_payload()[0]
+    # The report-type parameter should be "delivery-status", but it seems that
+    # some DSN generating MTAs don't include this on the Content-Type: header,
+    # so let's relax the test a bit.
+    if not msg.is_multipart() or msg.get_content_subtype() <> 'report':
+        return None
+    return check(msg)