repoze/repoze.sendmail — pull request #26 by moriyoshi (2013-08-19 14:21:42+00:00)
Title: Do not try to autodetect charset if the payload is already fancy-encoded (i.e. base64 or quoted-printable encoded)

It doesn't make much sense to try to autodetect the charset of the payload if the payload is already base64 or quoted-printable encoded.