mail·er
noun/ˈmeɪlə(r)/
/ˈmeɪlər/
- (especially North American English) (also mailing British and North American English)a letter or package that is sent by mail, especially one that is sent to a large number of people
邮件（尤指成批寄发的） - (North American English) an envelope, box, etc. for sending small things by mail
邮件封套（或小箱、盒等）