diff --git a/Doc/library/email.util.rst b/Doc/library/email.util.rst
--- a/Doc/library/email.util.rst
+++ b/Doc/library/email.util.rst
@@ -28,13 +28,18 @@
    *email address* parts.  Returns a tuple of that information, unless the parse
    fails, in which case a 2-tuple of ``('', '')`` is returned.
 
+   If the host name of the *email address* part is a IDN, it is automatically
+   decoded to unicode with the 'idna' codec.
+
 
 .. function:: formataddr(pair, charset='utf-8')
 
    The inverse of :meth:`parseaddr`, this takes a 2-tuple of the form ``(realname,
    email_address)`` and returns the string value suitable for a :mailheader:`To` or
    :mailheader:`Cc` header.  If the first element of *pair* is false, then the
-   second element is returned unmodified.
+   second element is returned unmodified.  If the host name of email_address
+   contains non-ASCII characters, it is automatically converted to a IDN
+   representation with the 'idna' codec.
 
    Optional *charset* is the character set that will be used in the :rfc:`2047`
    encoding of the ``realname`` if the ``realname`` contains non-ASCII
diff --git a/Lib/email/utils.py b/Lib/email/utils.py
--- a/Lib/email/utils.py
+++ b/Lib/email/utils.py
@@ -57,6 +57,17 @@
 
 # Helpers
 
+def _encode_decode_addr(addr, encode_codec, decode_codec):
+    """Helper function for formataddr() and parseaddr() to encode and
+    decode IDNAs.
+    """
+    parts = addr.split("@")
+    if len(parts) <= 1:
+        return addr
+    parts[-1] = parts[-1].encode(encode_codec).decode(decode_codec)
+    return "@".join(parts)
+
+
 def formataddr(pair, charset='utf-8'):
     """The inverse of parseaddr(), this takes a 2-tuple of the form
     (realname, email_address) and returns the string value suitable
@@ -65,12 +76,17 @@
     If the first element of pair is false, then the second element is
     returned unmodified.
 
+    If the host name of email_address contains non-ASCII characters,
+    it is automatically converted to a IDN representation with the
+    'idna' codec.
+
     Optional charset if given is the character set that is used to encode
     realname in case realname is not ASCII safe.  Can be an instance of str or
     a Charset-like object which has a header_encode method.  Default is
     'utf-8'.
     """
     name, address = pair
+    address = _encode_decode_addr(address, 'idna', 'ascii')
     # The address MUST (per RFC) be ascii, so throw a UnicodeError if it isn't.
     address.encode('ascii')
     if name:
@@ -208,7 +224,9 @@
     addrs = _AddressList(addr).addresslist
     if not addrs:
         return '', ''
-    return addrs[0]
+    name, address = addrs[0]
+    address = _encode_decode_addr(address, 'ascii', 'idna')
+    return name, address
 
 
 # rfc822.unquote() doesn't properly de-backslash-ify in Python pre-2.3.
diff --git a/Lib/test/test_email/test_email.py b/Lib/test/test_email/test_email.py
--- a/Lib/test/test_email/test_email.py
+++ b/Lib/test/test_email/test_email.py
@@ -2657,6 +2657,25 @@
             email.utils.make_msgid(domain='testdomain-string')[-19:],
             '@testdomain-string>')
 
+    def test_formataddr_encodes_idnas(self):
+        # issue 11783.  email parseaddr and formataddr should be IDNA aware
+        addr = "foo@d\u00f6m.ain"
+        puny = "foo@xn--dm-fka.ain"
+        self.assertEqual(utils.formataddr((None, addr)), puny)
+
+    def test_parseaddr_decodes_idnas(self):
+        # issue 11783.  email parseaddr and formataddr should be IDNA aware
+        puny = "Foo <bar@xn--dm-fka.ain>"
+        self.assertEqual(utils.parseaddr(puny), ("Foo", "bar@d\u00f6m.ain"))
+
+    def test_parseaddr_formataddr_ignore_idn_in_local_part_only(self):
+        # issue 11783.  email parseaddr and formataddr should be IDNA aware
+        addr = "xn--dm-fka"
+        name = "Foo"
+        pair = "%s <%s>" % (name, addr)
+        self.assertEqual(utils.parseaddr(pair), (name, addr))
+        self.assertEqual(utils.formataddr((name, addr)), pair)
+
 
 # Test the iterator/generators
 class TestIterators(TestEmailBase):