Re: [Exim] ACL config to reject mail from non standard DNS m…

At 10:39 am -0600 2004/02/27, mark david mcCreary wrote:
>I am trying to use Exim 4.30 ACL configuration to reject email that does
>not conform to Internet DNS standards, on the theory that a lot of spam
>is sent from zombie machines.
[...]
>2004-02-27 14:11:24 H=(hotmail.com) [64.4.11.15]
>F=<tunadave@???> rejected RCPT <mdm@???>:
>hotmail.com does not match name from reverse lookup of 64.4.11.15 -
>bay7-f15.bay7.hotmail.com
>
>
>Is there a way to apply regular expressions to the verify = helo so that
>the above will pass the verification process.
>

I give spam score points (so do not drop, unless there are other
reasons) to servers for which the reverse DNS and the HELO argument
do not agree in the last to parts of the domain. For instance a.b.c.d
would match e.c.d. Of course this is of not much use with countries
like the UK or Japan, but it helps a bit anyway.
Still there are a lot of legitimate senders that score on this rule
alone, they usually have a lot of groundless excuses and never fix
their servers.

Giuliano