Several years ago we had a problem with “bounce back” spam. Spammers were sending spam messages to the list, with return addresses of real people (addresses not on our list, just random email addresses). At its peak we were getting 300/hour. This did not sit well with spam blocking databases, as you would expect, or the people who got the bounced messages sent to their forged return addresses. We solved the problem in postfix by adding active filtering to incoming messages that analyzed the headers of the messages and just dropped ones that didn’t look right. The filters are quite complex, but they do the job nicely.

I wonder if there is a better way to do this today?

Larry

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Larry Finch

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