Updated base64mime encoder to use line lengths of 78 and fixed closing/flushing bug. Replaced quoted-printable encoding with base64 encoding.
Replaced base64 attacment encoding with base64mime encoding (splits lines).
Added wrapping of address list headers using whitespace folding. Fixed invalid charset in content-type header (UTF8 should have been utf-8).
Put back the generated boundaries and wrapped them to their oown line to ensure line length <= 78. Updated tests with a really long subject that should be wrapped, but currently isn't.