Re: Are SRV (Service) records normally consulted during mail delivery?

[Mail Man]

Thor Kottelin wrote:

> > is it normal, or usual, or typical, for a mail server to consult
> > a domain's SRV record (if it exists) to determine how to deliver
> > mail to that domain? Regardless if an MX record exists?
>
> No, as SMTP presently does not include such a provision.
>
> It might be beneficial for future SMTP versions to allow SRV usage,
> although the opportunity to run MX hosts on arbitrary ports would
> also involve new threats.

After noticing that the registrar that hosts my domains (network
solutions) allows me to set SRV records - including SMTP, I thought that
I might be able to outsmart spam zombies by setting my SRV-SMTP record
to indicate that my server accepts mail on some port other than 25.
Naturally, such a change would only be workable if all legit servers
consult SRV records when sending mail.

I discovered by accident a few years ago that having no MX record
actually worked as an anti-spam technique, because legit servers know to
fall back to the A record when mx lookup fails - but zombies don't do
that (my A record points to the same IP as my MX record would have). So
I'm thinking that zombies wouldn't also consult SRV records either.