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.
