On Mon, 9 Apr 2018 09:24:23 -0500
David Jones wrote:
> I was wondering if anyone knows of an SA plugin or another method to
> determine if the envelope-from domain has a valid MX record that is
> listening on TCP port 25. I don't think it would be a major scorer
> but it could be useful in meta rules.
There's NO_DNS_FOR_FROM which tests for MX or A. I don't know if it's
still true, but historically this has, in my experience, been largely a
surrogate test for made-up domains.
Having a single test for DNS and port 25 doesn't sound like a good
idea since you can't determine how much benefit come from each of the
two parts or score them separately.