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Exchange Online Protection: What is Backscatter Messages

What is Backscatter messages in Exchange Online Protection?


It’s the automated bounce messages which is sent by mail servers usually due to incoming spam.

Because Exchange Online Protection is a spam filtering service , messages sent to suspicious and non-existing recipients are rejected. When this process happens Exchange Online Protection generates a NDR ( non-delivery report) message to the sender. Because spammers frequently use a forged or invalid from address in their messages, the sender address to which the NDR is sent may result in a backscatter message. When this happens, outgoing servers that are associated with the EOP network may be listed on the  Backscatter DNS Block List (DNSBL). The Backscatter DNSBL is a list of IP addresses that send backscatter messages. It isn’t a spammer list, and the Exchange Online Protection team does not remove the servers from the Backscatter DNSBL.



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