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Configure server against backscatter spam at server level

Configure Postfix to block spam before it enters the server

Sep. 10, 2019 -

This month I had to deal with backscatter spam, affecting one of the mail servers I manage. As server engineer I make sure that servers don't send spam and that incoming email gets filtered. Despite all good efforts, this server kept being blacklisted for sending spam to iCloud, Office 365 and Google Gmail for Business (G Suite). Read along to find out how what caused this and how to fix this.

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Causing backscatter spam when the first mail server forwards email to another server that blocks message
Causing backscatter spam when the first mail server forwards email to another server that blocks message
Prevent backscatter spam by checking all messages before forwarding them to another server
Prevent backscatter spam by checking all messages before forwarding them to another server
Prevent backscatter bounce messages by responding with SMTP error codes instead
Prevent backscatter bounce messages by responding with SMTP error codes instead
Simple backscatter scenario, mail server bounces message to a falsified sender address
Simple backscatter scenario, mail server bounces message to a falsified sender address
Implementing stringent SMTP restrictions in Postfix - annotated screenshot from main.cf
Implementing stringent SMTP restrictions in Postfix - annotated screenshot from main.cf

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