Got rid of a FIXME and a generic Exception, opting instead for a CastException
Got rid of a FIXME and a generic Exception, opting instead for a CastException

If I get a bug report about the cast exception, then I can go from there
and figure out what other possibilities there are. It seems cleaner to
use this approach.

nachocove/MimeKit,jstedfast/MimeKit,jstedfast/MimeKit,nachocove/MimeKit,jstedfast/MimeKit,nachocove/MimeKit