Author: Marco Wessel Date: To: exim-users Subject: Re: [exim] How to send bounce messages just after error
On Mar 5, 2007, at 11:46 AM, lista_exim@??? wrote:
> Hi!
>
> When I receive a message to an false user of my system, I want to
> send a
> bounce message to the original sender just after the error, and I
> don't
> want Exim send the original message to the queue.
>
I used to do that because my incoming mx was only a frontend,
accepting all users for my domains and then trying to send them
onwards. It was a Bad Idea [tm]. (Rather, it was something I hadn't
thought about yet). It makes your queue fill up faster than a woman's
shopping cart in a discount store. At one point I had over 20000
(yes, twenty thousand) undeliverable bounces. Why? Because most spams
are sent with forged non-existent recipient addresses, and the
remainder is sent using forged recipient addresses that do exist. So
in essence:
- You send lots of people bounces who never sent you an e-mail in the
first place (forged existing recipient addresses)
- Your queue fills up with frozen messages because of all the bounces
that couldn't be delivered. (forged non-existent recipient addresses).
I now reject unknown sender addresses at MAIL time, and unknown
recipients at RCPT time. The only mails getting stuck on my queue now
are mails from locally submitted clients.
