Subject encoding on SmtpClient/MailMessage

This was confirmed as a bug in the MSDN forums:
http://social.msdn.microsoft.com/Forums/vstudio/en-US/4d1c1752-70ba-420a-9510-8fb4aa6da046/subject-encoding-on-smtpclientmailmessage

And a bug was filed on Microsoft Connect: https://connect.microsoft.com/VisualStudio/feedback/details/785710/mailmessage-subject-incorrectly-encoded-in-utf-8-base64

One work-around is to set the SubjectEncoding of the MailMessage to an other encoding, such as ISO-8859-1. In this case, the subject will be encoded in Quoted Printable (not Base64) which avoids the problem.

A better solution is to use Encoding.Unicode instead of Encoding.UTF8 for the SubjectEncoding.

It appears that, as the Microsoft implementation simply ignores the reality of UTF-16 being able to encode characters in more than two bytes (as seen on Why does C# use UTF-16 for strings?), the stable character size helps.

I've seen this used on https://gist.github.com/dbykadorov/9047455.