mail bomb
noun /ˈmeɪl bɒm/
/ˈmeɪl bɑːm/
- (North American English) (also letter bomb British and North American English)a small bomb that is sent to somebody hidden in a letter that explodes when the envelope is opened
书信炸弹（匿藏在书信中，开封即爆炸） - an extremely large number of email messages that are sent to somebody
电邮轰炸（指发给某人的超大量电子邮件）