这个纸质信封很适合用作邮寄文件的邮件包装。

This paper ___mailer is perfect for sending documents.

这家公司聘请了一家专业的邮寄服务商来发送他们的产品目录。

The company hired a professional ___mailer to send out their product catalogs.

这款邮件群发软件可以同时向数千名客户发送促销信息。

This ___mailer can send promotional messages to thousands of customers at once.