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What is backscatter mail?

April 26, 2017backscatter mail

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What is backscatter mail?

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When a spammer or worm sends mail with forged sender addresses, innocent sites are flooded with undeliverable mail notifications. This is called backscatter mail. With Postfix, you know that you’re a backscatter victim when your logfile goes on and on like this: Dec 4 04:30:09 hostname postfix/smtpd[58549]: NOQUEUE: reject: RCPT from xxxxxxx[x.x.x.x]: 550 5.1.1 : Recipient address rejected: User unknown; from=<> to= proto=ESMTP helo= What you see are lots of “user unknown” errors with “from=<>“. These are error reports from MAILER-DAEMONs elsewhere on the Internet.