DNS question, null MX records

Eric J Esslinger eesslinger at fpu-tn.com
Tue Dec 15 09:46:06 CST 2009


I've had a couple of off-list comments already about using it as/donating it to a spam trap; That is a good idea and I actually thought of that.

However, the address was formerly used for email addresses for our customers and for our business (some 10 years ago it was registered, but has not had any valid dns records set for roughly 6 years), and we still deal from time to time with mail being sent to old addresses on that domain for various reasons (several dns registrations, for example, we've had to help these people go through the fax change system because we don't want to go to the trouble of setting up to receive email on this domain again)

So in any case, due to customer privacy concerns we feel we can't do that.

Also I have set the spf -all on it, for those that look for these records to auot-reject email from the domain.
__________________________
Eric Esslinger
Information Services Manager - Fayetteville Public Utilities
http://www.fpu-tn.com/
(931)433-1522 ext 165



-----Original Message-----
From: Eric J Esslinger [mailto:eesslinger at fpu-tn.com]
Sent: Tuesday, December 15, 2009 9:18 AM
To: 'nanog at nanog.org'
Subject: DNS question, null MX records


I have a domain that exists solely to cname A records to another domain's websites. There is no MX server for that domain, there is no valid mail sent as from that domain. However when I hooked it up I immediately started getting bounces and spam traffic attemtping to connect to the cnamed A record, which has no inbound mail server (It's actually hitting the firewall in front of it). (The domain name is actually several years old and has been sitting without dns for a while)

I found a reference to a null MX proposal, constructed so:
example.com    IN    MX 0 .

Question: Is this a valid dns construct or did the proposal die? I don't want to cause people problems but at the same time, I don't want any of this crap to even attempt to deliver on this domain to any of my servers.


__________________________
Eric Esslinger
Information Services Manager - Fayetteville Public Utilities http://www.fpu-tn.com/ (931)433-1522 ext 165



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