the email.* package seems to over-encode international charset address fields - resulting even in display errors in the receivers reader - , 
when message header composition is done as recommended in http://docs.python.org/library/email.header.html 

Python 2.7.2
>>> e=email.Parser.Parser().parsestr(getcliptext())
>>> e['From']
'=?utf-8?q?Martin_v=2E_L=C3=B6wis?= <report@bugs.python.org>'
# note the par
>>> email.Header.decode_header(_)
[('Martin v. L\xc3\xb6wis', 'utf-8'), ('<report@bugs.python.org>', None)]
# unfortunately there is no comfortable function for this:
>>> u='Martin v. L\xc3\xb6wis'.decode('utf8') + ' <report@bugs.python.org>'
>>> u
u'Martin v. L\xf6wis <report@bugs.python.org>'
>>> msg=email.Message.Message()
>>> msg['From']=u
>>> msg.as_string()
'From: =?utf-8?b?TWFydGluIHYuIEzDtndpcyA8cmVwb3J0QGJ1Z3MucHl0aG9uLm9yZz4=?=\n\n'
>>> msg['From']=str(u)
>>> msg.as_string()
'From: =?utf-8?b?TWFydGluIHYuIEzDtndpcyA8cmVwb3J0QGJ1Z3MucHl0aG9uLm9yZz4=?=\nFrom: Martin v. L\xf6wis <report@bugs.python.org>\n\n'
>>> msg['From']=email.Header.Header(u)
>>> msg.as_string()
'From: =?utf-8?b?TWFydGluIHYuIEzDtndpcyA8cmVwb3J0QGJ1Z3MucHl0aG9uLm9yZz4=?=\nFrom: Martin v. L\xf6wis <report@bugs.python.org>\nFrom: =?utf-8?b?TWFydGluIHYuIEzDtndpcyA8cmVwb3J0QGJ1Z3MucHl0aG9uLm9yZz4=?=\n\n'
>>> 

(BTW: strange is that multiple msg['From']=... _assignments_ end up as multiple additions !???   also msg renders 8bit header lines without warning/error or auto-encoding, while it does auto on unicode!??)

Whats finally arriving at the receiver is typically like:

From: "=?utf-8?b?TWFydGluIHYuIEzDtndpcyA8cmVwb3J0QGJ1Z3MucHl0aG9uLm9yZz4=?=" <report@bugs.python.org>

because the servers seem to want the address open, they extract the address and _add_ it (duplicating) as ASCII. => error

I have not found any emails in my archives where address header fields are so over-encoded like python does. Even in non-address fields mostly only those words/groups are encoded which need it.

I assume the sophisticated/high-level looking email.* package doesn't expect that the user fiddles things together low-level? with parseaddr, re.search, make_header Header.encode , '.join ... Or is it indeed (undocumented) so? IMHO it should be auto-smart enough.

Note: there is a old deprecated function mimify.mime_encode_header which seemed to try to cautiously auto-encode correct/sparsely (but actually fails too on all examples tried).