instance method new_port

# File actionmailer/lib/action_mailer/vendor/tmail-1.2.7/tmail/mailbox.rb, line 428
    def new_port
      fname = nil
      tmpfname = nil
      newfname = nil

      begin
        fname = "#{Time.now.to_i}.#{$$}_#{Maildir.unique_number}.#{Socket.gethostname}"
        
        tmpfname = "#{@tmp}/#{fname}"
        newfname = "#{@new}/#{fname}"
      end while FileTest.exist? tmpfname

      if block_given?
        File.open(tmpfname, 'w') {|f| yield f }
        File.rename tmpfname, newfname
        PORT_CLASS.new(newfname)
      else
        File.open(tmpfname, 'w') {|f| f.write "\n\n" }
        PORT_CLASS.new(tmpfname)
      end
    end