diff -r a47996c10579 Lib/smtpd.py
--- a/Lib/smtpd.py	Wed Aug 06 18:55:54 2014 +0300
+++ b/Lib/smtpd.py	Wed Aug 06 23:07:29 2014 +0200
@@ -657,31 +657,43 @@
 
 
 class DebuggingServer(SMTPServer):
-    # Do something with the gathered message
-    def process_message(self, peer, mailfrom, rcpttos, data):
+    def _print_message_content(self, peer, data):
         inheaders = 1
+        if type(data) == bytes:
+            # Preserve newlines and cut off "b''":
+            data = str(data).replace('\\n', '\n')[2:-1]
         lines = data.split('\n')
-        print('---------- MESSAGE FOLLOWS ----------')
         for line in lines:
             # headers first
             if inheaders and not line:
                 print('X-Peer:', peer[0])
                 inheaders = 0
             print(line)
+
+    # Do something with the gathered message
+    def process_message(self, peer, mailfrom, rcpttos, data):
+        inheaders = 1
+        print('---------- MESSAGE FOLLOWS ----------')
+        self._print_message_content(peer, data)
         print('------------ END MESSAGE ------------')
 
 
 class PureProxy(SMTPServer):
     def process_message(self, peer, mailfrom, rcpttos, data):
-        lines = data.split('\n')
+        x_peer_header = 'X-Peer: %s' % peer[0]
+        newline = NEWLINE
+        if isinstance(data, bytes):
+            x_peer_header = x_peer_header.encode()
+            newline = NEWLINE.encode()
+        lines = data.split(newline)
         # Look for the last header
         i = 0
         for line in lines:
             if not line:
                 break
             i += 1
-        lines.insert(i, 'X-Peer: %s' % peer[0])
-        data = NEWLINE.join(lines)
+        lines.insert(i, x_peer_header)
+        data = newline.join(lines)
         refused = self._deliver(mailfrom, rcpttos, data)
         # TBD: what to do with refused addresses?
         print('we got some refusals:', refused, file=DEBUGSTREAM)