DNS question, null MX records

Dave Sparro dsparro at gmail.com
Tue Dec 15 09:45:09 CST 2009

On 12/15/2009 10:17 AM, Eric J Esslinger wrote:
> 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.

Pulling from my often mangled memory:

This was proposed in a draft RFC that went nowhere.
Parsing the Null MX record was implemented in at least one fairly 
popular MTA (Postfix?)
The null MX record was published by whoever got (some of?) the Excite 
@Home domain(s) after that company flamed out.  This results in the 
occasional post to various mailing lists by people wondering why they 
are queuing mail bound for said domain.

So to the point of your question, it may reduce some SMTP connection 
attempts to you, but will not likely eliminate them.


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