Re: [Exim] STOP - mail from <> emails

Hi Schalk!

> My question is, how can I block <> senders and recipients with Exim, or do I
> need a Spam filter?

That wouldn't be a sensible thing to do, because these messages are
error messages, and in your case, most likely created by your own
Exim.

> Also, how are Spammers able to relay through my server? Since I only allow
> relaying for certain IP's and domains. Or are they intelligent enough to
> relay mails using the same host name (server name)?

No, spammers are dumb by definition. What's happening to you is that
they try to send mail to invalid/non-existent addresses in your
domain. Usually, these would be rejected at RCPT time. But your Exim
actually accepts these mails, finds out that they are unroutable, and
creates an error message. This error is bounced back using the "<>"
address and sent to whoever appeared to be the originator of the spam
(either a forged return-path, or sometimes the intended victim of the
spammer).

The solution would be to set receiver_verify in your Exim 3 config.
There are also a few related options, which you might check out in the
spec or in the Exim 3 book (Chapter 13: Message Reception and Policy
Controls).

Andy