I got UnicodeError when I use iso-2022-jp(7bit) for mail encoding.
following message was displayed.

  Edit Error: 'iso2022_jp' codec can't decode byte 0xe3 in position 11:
illegal multibyte sequence

And some incorrect mail headers are found when I use utf-8. 

  From:
=?utf-8?b?566h55CG6ICFIDxpc3N1ZV90cmFja2VyQGxvY2FsaG9zdD4=?=@localhost.localdomain

This should be:

  From: =?utf-8?b?566h55CG6ICF?= <issue_tracker@localhost.localdomain>