quoted_printable_encode_header (MailFactory)

    # File lib/mailfactory.rb, line 413
      def quoted_printable_encode_header(text)
        text.enum_for(:each_byte).map do |ord|
          if ord < 128 and ord != 61 # 61 is ascii '='
            ord.chr
          else
            '=%X' % ord
          end
        end.join('').
            chomp.
            gsub(/=$/,'').
            gsub('?', '=3F').
            gsub('_', '=5F').
            gsub(/ /, '_')
      end