Backscatter (email)
（重定向自Backscatter spam）
Backscatter (also known as outscatter, misdirected bounces, blowback or collateral spam) is incorrectly automated bounce messages sent by mail servers, typically as a side effect of incoming spam.
Recipients of such messages see them as a form of unsolicited bulk e-mail or spam since they were not solicited by the recipients, are substantially similar to each other and are delivered in bulk quantities. Systems that generate e-mail backscatter may be listed on various DNS-based Blackhole Lists and may be in violation of internet service providers' Terms of Service.