From c498829e94cafdc194a45eaf49d4f75785ac0a7a Mon Sep 17 00:00:00 2001
From: Mark Sapiro <mark@msapiro.net>
Date: Tue, 23 May 2017 12:45:06 -0700
Subject: Implement base64 encoded recipient header.

---
 Mailman/Defaults.py.in         | 11 +++++++++++
 Mailman/Handlers/SMTPDirect.py |  5 +++++
 NEWS                           |  7 +++++++
 3 files changed, 23 insertions(+)

diff --git a/Mailman/Defaults.py.in b/Mailman/Defaults.py.in
index 7a2dc526..e6738192 100755
--- a/Mailman/Defaults.py.in
+++ b/Mailman/Defaults.py.in
@@ -629,6 +629,17 @@ NNTP_REWRITE_DUPLICATE_HEADERS = [
 # 3 -> always remove, rename and preserve original DKIM headers.
 REMOVE_DKIM_HEADERS = No
 
+# If the following is set to a non-empty string, that string is the name of a
+# header that will be added to personalized and VERPed deliveries with value
+# equal to the base64 encoding of the recipient's email address.  This is
+# intended to enable identification of the recipient otherwise redacted from
+# "spam report" feedback loop messages.  For example, if
+# RCPT_BASE64_HEADER_NAME = 'X-Mailman-R-Data'
+# a header like
+# X-Mailman-R-Data: dXNlckBleGFtcGxlLmNvbQo=
+# will be added to messages sent to user@@example.com.
+RCPT_BASE64_HEADER_NAME = ''
+
 # All `normal' messages which are delivered to the entire list membership go
 # through this pipeline of handler modules.  Lists themselves can override the
 # global pipeline by defining a `pipeline' attribute.
diff --git a/Mailman/Handlers/SMTPDirect.py b/Mailman/Handlers/SMTPDirect.py
index 3b489c2f..ca6aebdd 100644
--- a/Mailman/Handlers/SMTPDirect.py
+++ b/Mailman/Handlers/SMTPDirect.py
@@ -30,6 +30,7 @@ import copy
 import time
 import socket
 import smtplib
+from base64 import b64encode
 from types import UnicodeType
 
 from Mailman import mm_cfg
@@ -371,6 +372,10 @@ def verpdeliver(mlist, msg, msgdata, envsender, failures, conn):
         del msgcopy['x-mailman-copy']
         if msgdata.get('add-dup-header', {}).has_key(recip):
             msgcopy['X-Mailman-Copy'] = 'yes'
+        # If desired, add the RCPT_BASE64_HEADER_NAME header
+        if len(mm_cfg.RCPT_BASE64_HEADER_NAME) > 0:
+            del msgcopy[mm_cfg.RCPT_BASE64_HEADER_NAME]
+            msgcopy[mm_cfg.RCPT_BASE64_HEADER_NAME] = b64encode(recip)
         # For the final delivery stage, we can just bulk deliver to a party of
         # one. ;)
         bulkdeliver(mlist, msgcopy, msgdata, envsender, failures, conn)
diff --git a/NEWS b/NEWS
index 2bd0e9b0..9c38b72e 100644
--- a/NEWS
+++ b/NEWS
@@ -15,6 +15,13 @@ Here is a history of user visible changes to Mailman.
 
   New Features
 
+    - There is a new RCPT_BASE64_HEADER_NAME setting.  If this is set to a
+      non-empty string, that string is the name of a header that will be added
+      to personalized and VERPed deliveries with value equal to the base64
+      encoding of the recipient's email address.  This is intended to enable
+      identification of the recipient otherwise redacted from "spam report"
+      feedback loop messages.
+
     - cron/senddigests has a new -e/--exceptlist option to send pending
       digests for all but a named list.  (LP: #1619770)
 
-- 
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