convert_to (TMail::Unquoter)

    # File lib/action_mailer/vendor/tmail-1.1.0/tmail/quoting.rb, line 97
            def convert_to(text, to, from)
              return text unless to && from
              text ? Iconv.iconv(to, from, text).first : ""
            rescue Iconv::IllegalSequence, Iconv::InvalidEncoding, Errno::EINVAL
              # the 'from' parameter specifies a charset other than what the text
              # actually is...not much we can do in this case but just return the
              # unconverted text.
              #
              # Ditto if either parameter represents an unknown charset, like
              # X-UNKNOWN.
              text
            end