Jim Lang put forth on 11/16/2009 2:00 PM: > Wietse Venema wrote: >> Jim Lang: >> >>> OK here is the scenario. >>> Spammer sends mail to: u...@myclientsdomain.com from forged address >>> vic...@randomdomain.com >>> >>> If u...@myclientsdomain.com is delivered locally, not a problem, if >>> the address is invalid, postix rejects the mail during the smtp >>> connection. >>> >>> But if u...@myclientsdomain.com is an alias to >>> mycli...@otherserver.com, postfix accepts the mail as deliverable and >>> forwards it to hotmail.com. >>> But if mycli...@otherserver.com can for whatever reason not be >>> delivered, otherserver.com does what it is supposed to do and rejects >>> the mail during the smtp connection, which causes postfix to send out >>> a non-delivery report to vic...@randomdomain.com -- backscatter. >>> >>> Is there a way to stop this? >> >> Yes. Don't forward SPAM. >> >> Wietse >> > And how do I do that in this scenario?
You don't do it "in this scenario". You set up comprehensive spam rejection techniques, one of which is identifying forged email, and reject spam when it hits your MX. Dozens of books have been written, and dozens of email lists are maintained, specifically for fighting spam. The answer to your scenario isn't a simple one paragraph response on postfix-users. What are you doing up to this point to reject spam at your border MX(s)? -- Stan
