diff -r 61aa76adca20 Lib/email/mime/text.py
--- a/Lib/email/mime/text.py	Thu Mar 22 10:40:20 2012 -0400
+++ b/Lib/email/mime/text.py	Thu Mar 22 13:57:49 2012 -0400
@@ -9,7 +9,6 @@
 from email.encoders import encode_7or8bit
 from email.mime.nonmultipart import MIMENonMultipart
 
-
 
 class MIMEText(MIMENonMultipart):
     """Class for generating text/* type MIME documents."""
@@ -27,4 +26,12 @@
         """
         MIMENonMultipart.__init__(self, 'text', _subtype,
                                   **{'charset': _charset})
+
+        try:
+            _text.encode(_charset)
+        except UnicodeEncodeError:
+            if _charset!='us-ascii':
+                raise
+            _charset = 'utf-8'
+
         self.set_payload(_text, _charset)
diff -r 61aa76adca20 Lib/test/test_email/test_email.py
--- a/Lib/test/test_email/test_email.py	Thu Mar 22 10:40:20 2012 -0400
+++ b/Lib/test/test_email/test_email.py	Thu Mar 22 13:57:49 2012 -0400
@@ -617,6 +617,19 @@
             abc
             """))
 
+    def test_unicode_body_defaults_to_utf8_encoding(self):
+        # Issue 14291
+        m = MIMEText('É testabc\n')
+        self.assertEqual(str(m),textwrap.dedent("""\
+            MIME-Version: 1.0
+            Content-Type: text/plain; charset="utf-8"
+            Content-Transfer-Encoding: base64
+
+            w4kgdGVzdGFiYwo=
+            """))
+
+
+
 # Test the email.encoders module
 class TestEncoders(unittest.TestCase):
 
@@ -642,7 +655,7 @@
         eq(msg['content-transfer-encoding'], '7bit')
         # Similar, but with 8bit data
         msg = MIMEText('hello \xf8 world')
-        eq(msg['content-transfer-encoding'], '8bit')
+        eq(msg['content-transfer-encoding'], 'base64')
         # And now with a different charset
         msg = MIMEText('hello \xf8 world', _charset='iso-8859-1')
         eq(msg['content-transfer-encoding'], 'quoted-printable')
diff -r 61aa76adca20 Lib/test/test_email/torture_test.py
--- a/Lib/test/test_email/torture_test.py	Thu Mar 22 10:40:20 2012 -0400
+++ b/Lib/test/test_email/torture_test.py	Thu Mar 22 13:57:49 2012 -0400
@@ -10,10 +10,10 @@
 import os
 import unittest
 from io import StringIO
-from types import ListType
 
-from email.test.test_email import TestEmailBase
-from test.support import TestSkipped, run_unittest
+from test.test_email import TestEmailBase
+from unittest.case import SkipTest
+from test.support import run_unittest
 
 import email
 from email import __file__ as testfile
@@ -28,7 +28,7 @@
 try:
     openfile('crispin-torture.txt')
 except IOError:
-    raise TestSkipped
+    raise SkipTest
 
 
 
@@ -50,10 +50,10 @@
         neq = self.ndiffAssertEqual
         msg = self._msgobj('crispin-torture.txt')
         payload = msg.get_payload()
-        eq(type(payload), ListType)
+        eq(type(payload), list)
         eq(len(payload), 12)
-        eq(msg.preamble, None)
-        eq(msg.epilogue, '\n')
+        eq(msg.preamble, '')
+        eq(msg.epilogue, '')
         # Probably the best way to verify the message is parsed correctly is to
         # dump its structure and compare it against the known structure.
         fp = StringIO()