[Mimedefang] sending relay has no MX record?

Lee Dilkie Lee at dilkie.com
Mon Jan 31 08:26:43 EST 2005

Kevin A. McGrail wrote:

> I believe an MX was designed as a Mail Gateway record for machines not 
> directly connected to the network.  Therefore, since an A record is 
> for machines that are connected to the network, an A record should be 
> enough to allow for mail to be delivered.
> I know in practice that using only an A record works and is frowned 
> upon.  I also know that an MX record has been expanded more and more.  
> But from an RFC perspective though, I'm not sure it's "incorrect" to 
> just use an A record without an MX record.  Hopefully someone else can 
> comment but in the meantime, I'm not sure it's a legitimate test for 
> spaminess.
> Sincerely,
>> Am seeing some spam where the sender's From_ address's domain
>> doesn't have an MX record.  Was considering noting that fact
>> in the header as an extra X- field, and then letting SA score
>> it negatively. Has anyone tried that sort of thing?  Can
>> you offer some prototype code that does something like that? 
I think Gary asking something different. He wants to check if the "from" 
domain has an MX record.

I think this is a valid test, as how could you send an NDR to such a 
domain, and a simple "reply" obviously wouldn't work so well.

I wouldn't think you'd get many hits on this sort of test, anyone who's 
gone through the trouble of setting up a domain has probably also 
defined an MX record. But let us know if you do get any hits, I'm curious.


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