create_mail

# File actionmailer/lib/action_mailer/old_api.rb, line 142
    def create_mail
      m = @_message

      set_fields!({:subject => @subject, :to => @recipients, :from => @from,
                   :bcc => @bcc, :cc => @cc, :reply_to => @reply_to}, @charset)

      m.mime_version = @mime_version    if @mime_version
      m.date         = @sent_on.to_time rescue @sent_on if @sent_on

      @headers.each { |k, v| m[k] = v }

      real_content_type, ctype_attrs = parse_content_type
      main_type, sub_type = split_content_type(real_content_type)

      if @parts.size == 1 && @parts.first.parts.empty?
        m.content_type([main_type, sub_type, ctype_attrs])
        m.body = @parts.first.body.encoded
      else
        @parts.each do |p|
          m.add_part(p)
        end

        m.body.set_sort_order(@implicit_parts_order)
        m.body.sort_parts!

        if real_content_type =~ /multipart/
          ctype_attrs.delete "charset"
          m.content_type([main_type, sub_type, ctype_attrs])
        end
      end

      wrap_delivery_behavior!
      m.content_transfer_encoding = '8bit' unless m.body.only_us_ascii?

      @_message
    end