SRV records (was Re: [Mimedefang] OT: www. and "lazy users")

[David F. Skoll]

Jeff Rife wrote:

> But, would this be good or bad in the context of this list (i.e., mail 
> filtering)?

> With a zombied PC able to use SRV records to determine that domain.tld 
> has their incoming mail server listening on port 2525, e-mail spam and 
> virii will flow even more freely than they do now.

It would be good or bad, depending on your viewpoint. :-)

If an ISP does not wish to permit this kind of thing, it could
restrict DNS queries to its own DNS servers, and they could return a
record of smtp-out.paranoid-isp.com for all SRV queries for SMTP
servers.  This would achieve the goal of having outbound mail flow
through the ISP's servers.  (I suppose if you somehow knew the IP
address and port of a listening external SMTP server, you could
connect, but that wouldn't be feasible for spambots.)

Regards,

David.