diff -r fd53f083768c Lib/smtpd.py
--- a/Lib/smtpd.py	Sat Mar 08 21:40:29 2014 -0500
+++ b/Lib/smtpd.py	Wed Apr 02 13:37:08 2014 +0200
@@ -136,6 +136,7 @@
         self.received_data = ''
         self.fqdn = socket.getfqdn()
         self.num_bytes = 0
+        self.decode_data = True
         try:
             self.peer = conn.getpeername()
         except OSError as err:
@@ -287,7 +288,10 @@
             return
         elif limit:
             self.num_bytes += len(data)
-        self.received_lines.append(str(data, "utf-8"))
+        if self.decode_data == True:    
+            self.received_lines.append(str(data, "utf-8"))
+        else:
+            self.received_lines.append(data)
 
     # Implementation of base class abstract method
     def found_terminator(self):
@@ -319,6 +323,8 @@
             method(arg)
             return
         else:
+            if self.decode_data == False:
+                self.received_lines.append(str(line,"utf-8"))    
             if self.smtp_state != self.DATA:
                 self.push('451 Internal confusion')
                 self.num_bytes = 0