Friday 15 May 2009

FAQ: Suffering Backscatter

Dear Richi, I have about 20-30 returned emails from some entity/person who is somehow using my domain to send out bulk email. How is that even possible?

Sadly, it's trivial for a spammer to forge your address. It's not your Web host's fault.

Some badly configured email servers auto-reply to spam. That's what you're seeing.

If you want to complain to anyone, complain to the people running the servers who are auto-replying to you. Here's a template complaint I've used before...
Hello. You are sending spam to me by bouncing spam to an unrelated person. I did not send the spam to your server: spammers forge the message sender. Hence, your reply goes to an innocent third party.

Perhaps you sent an unsolicited bounce because your mail server is incorrectly configured. Please don't do that. You should *reject* during the SMTP conversation, not *bounce* after accepting the spam message. It is not necessary for your MTA to send a non-delivery DSN -- you should reject at the point of SMTP RCPT with a 553 error or equivalent.

Or perhaps you're auto-replying to spam. Presumably you filter spam before delivering inbound email. In which case, this reply shows that spam is getting through those filters.

It's bad practice to accept a message for a non-existent user. If you accept and then bounce, you're sending spam. For more information, please see

If this was an isolated error, there's no need to be concerned that you will be blacklisted as a spam source. It usually takes several complaints to illustrate a pattern of email abuse.

However, I urge you to correctly configure your mail servers.
More info at an old post of mine: I Got 25,000 Spam Messages in Two Days!

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