diff -r a377a4298b4e Lib/email/generator.py
--- a/Lib/email/generator.py	Wed Aug 22 23:27:26 2012 -0700
+++ b/Lib/email/generator.py	Fri Aug 24 01:56:10 2012 +0800
@@ -348,6 +348,9 @@
 
     The outfp object must accept bytes in its write method.
     """
+    def __init__(self, outfp, mangle_from_ = True, maxheaderlen = 78):
+        Generator.__init__(self, outfp, mangle_from_, maxheaderlen)
+
 
     # Bytes versions of this constant for use in manipulating data from
     # the BytesIO buffer.
@@ -391,6 +394,8 @@
         if msg._payload is None:
             return
         if _has_surrogates(msg._payload):
+            if self._mangle_from_:
+                msg._payload = fcre.sub(">From ", msg._payload)
             self.write(msg._payload)
         else:
             super(BytesGenerator,self)._handle_text(msg)