1 files changed, 21 insertions, 1 deletions

diff --git a/src/mailman_pgp/utils/email.py b/src/mailman_pgp/utils/email.py
index 80cf83f..d1efc40 100644
--- a/src/mailman_pgp/utils/email.py
+++ b/src/mailman_pgp/utils/email.py
@@ -36,11 +36,31 @@ def copy_headers(from_msg, to_msg, overwrite=False):
             del to_msg[key]
         if key not in to_msg:
             to_msg[key] = value
-    if to_msg.get_unixfrom() is None:
+    if to_msg.get_unixfrom() is None or overwrite:
         to_msg.set_unixfrom(from_msg.get_unixfrom())
 
 
 @public
+def overwrite_message(from_msg, to_msg):
+    """
+    Overwrite message data of `to_msg` with that of `from_msg`.
+
+    :param from_msg: The source `Message`.
+    :type from_msg: email.message.Message
+    :param to_msg: The destination `Message`.
+    :type to_msg: email.message.Message
+    """
+    del to_msg[:]
+    for key, value in from_msg.items():
+        to_msg[key] = value
+    to_msg.set_unixfrom(from_msg.get_unixfrom())
+    to_msg.set_payload(from_msg.get_payload(), from_msg.get_charset())
+    to_msg.preamble = from_msg.preamble
+    to_msg.epilogue = from_msg.epilogue
+    to_msg.set_default_type(from_msg.get_default_type())
+
+
+@public
 def get_email(msg):
     display_name, email = parseaddr(msg['from'])
     # Address could be None or the empty string.