diff -r e408e821d6c8 Lib/email/message.py
--- a/Lib/email/message.py	Sat Jul 27 02:41:48 2013 +0200
+++ b/Lib/email/message.py	Sat Jul 27 13:01:59 2013 +0800
@@ -275,6 +275,28 @@
         Optional charset sets the message's default character set.  See
         set_charset() for details.
         """
+        cte = str(self.get('content-transfer-encoding', '')).lower()
+        if isinstance(payload, bytes) and cte:
+            if cte == 'base64':
+                try:
+                    decode_b(b''.join(payload.splitlines()))
+                except AssertionError:
+                    raise ValueError('Can not set payload with invalid '
+                                     'base64 data if content transfer '
+                                     'encoding is base64.')
+            elif cte in ('x-uuencode', 'uuencode', 'uue', 'x-uue'):
+                in_file = BytesIO(payload)
+                out_file = BytesIO()
+                try:
+                    uu.decode(in_file, out_file, quiet=True)
+                except uu.Error:
+                    # Some decoding problem
+                    pass
+                except binascii.Error:
+                    raise ValueError('Can not set payload with invalid ' +
+                                     '%s data if content transfer ' % cte +
+                                     'encoding is %s.' % cte)
+            payload = payload.decode('ascii', 'surrogateescape')
         self._payload = payload
         if charset is not None:
             self.set_charset(charset)
diff -r e408e821d6c8 Lib/test/test_email/test_email.py
--- a/Lib/test/test_email/test_email.py	Sat Jul 27 02:41:48 2013 +0200
+++ b/Lib/test/test_email/test_email.py	Sat Jul 27 13:01:59 2013 +0800
@@ -593,6 +593,72 @@
             "attachment; filename*=utf-8''Fu%C3%9Fballer%20%5Bfilename%5D.ppt",
             msg['Content-Disposition'])
 
+    def test_binary_quopri_payload(self):
+        def quopri_set_payload(binary_data, expected_data):
+            msg = Message()
+            msg['content-type'] = 'text/plain; charset=latin-1'
+            msg['content-transfer-encoding'] = 'quoted-printable'
+            msg.set_payload(binary_data)
+            self.assertEqual(msg.get_payload(decode=True), expected_data)
+        quopri_set_payload(b'foo=e6=96=87bar', b'foo\xe6\x96\x87bar')
+        quopri_set_payload(b'\x00\u1234\xff\377', b'\x00\u1234\xff\377')
+        quopri_set_payload(b'Hello world', b'Hello world')
+        quopri_set_payload(b'', b'')
+        quopri_set_payload(b'foo=ez6=!96=87bar', b'foo=ez6=!96\x87bar')
+        bytes_data = 'Fußballer.ppt'.encode('utf-8')
+        quopri_set_payload(bytes_data, bytes_data)
+
+    def test_binary_base64_payload(self):
+        def base64_set_payload(binary_data, expected_data):
+            msg = Message()
+            msg['content-type'] = 'text/plain; charset=latin-1'
+            msg['content-transfer-encoding'] = 'base64'
+            msg.set_payload(binary_data)
+            self.assertEqual(msg.get_payload(decode=True), expected_data)
+        def base64_set_payload_raise_exception(binary_data):
+            msg = Message()
+            msg['content-type'] = 'text/plain; charset=latin-1'
+            msg['content-transfer-encoding'] = 'base64'
+            self.assertRaises(ValueError, msg.set_payload, binary_data)
+        base64_set_payload(b'Zm9v5paHYmFy', b'foo\xe6\x96\x87bar')
+        base64_set_payload(b'Hello world', b'\x1d\xe9e\xa3\n+\x95')
+        base64_set_payload(b'', b'')
+        base64_set_payload('Fußballer.ppt'.encode('utf-8'),
+                           b'\x16\xe6\xda\x96W\xab\xa6\x9b')
+        base64_set_payload_raise_exception(b'Zm9h(v5pa*HYmFy')
+        base64_set_payload_raise_exception(b'\x00\u1234\xff\377')
+
+    def test_binary_uuencode_payload(self):
+        def uuencode_set_payload(binary_data, expected_data, encoding):
+            msg = Message()
+            msg['content-type'] = 'text/plain; charset=latin-1'
+            msg['content-transfer-encoding'] = encoding
+            msg.set_payload(binary_data)
+            self.assertEqual(msg.get_payload(decode=True),
+                             expected_data,
+                             'get_payload returns wrong result '
+                             'with encoding %s.' % encoding)
+        def uuencode_set_payload_raise_exception(binary_data,
+                                                 encoding):
+            msg = Message()
+            msg['content-type'] = 'text/plain; charset=latin-1'
+            msg['content-transfer-encoding'] = encoding
+            self.assertRaises(ValueError, msg.set_payload, binary_data)
+        for encoding in ('x-uuencode', 'uuencode', 'uue', 'x-uue'):
+            uuencode_set_payload(b"begin 666 -\n)9F]OYI:'8F%R\n \nend\n",
+                                 b'foo\xe6\x96\x87bar',
+                                 encoding)
+            uuencode_set_payload(b'\x00\u1234\xff\377',
+                                 b'\x00\u1234\xff\377',
+                                 encoding)
+            uuencode_set_payload(b'Hello world', b'Hello world', encoding)
+            uuencode_set_payload(b'', b'', encoding)
+            bytes_data = 'Fußballer.ppt'.encode('utf-8')
+            uuencode_set_payload(bytes_data, bytes_data, encoding)
+            uuencode_set_payload_raise_exception(
+                    b"begin 777 -\n)9Z]OYI:'iF%R\n \nend\n",
+                    encoding)
+
     def test_add_header_with_name_only_param(self):
         msg = Message()
         msg.add_header('Content-Disposition', 'inline', foo_bar=None)