spf-discuss
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Re: implicit mx rule

2004-06-18 14:59:31
On Fri, 18 Jun 2004 17:39:53 -0400, Meng Weng Wong wrote:

On Fri, Jun 18, 2004 at 10:31:44PM +0100, Karl Prince wrote:
| > Personally, I don't think the above should be necessary.  I
| > think that if you get mail from a return-path that has only
| > an A record and neither an MX record nor an SPF record, you
| > should assume that it's not meant to be an MTA.  This rule
| > subsumes the MTAMark semantic.
| 
| I disagree, with your proposed rule above for return-path 
| without an MX or SPF, but with A (and matching PTR I assume)
| 
| The RFC I can't quote off the top of my head, but I thought 
| that a receiving MTA (and therefore sending MTA) could get away 
| with just an A record for the Domain (giving a weight of 0), if 
| no MX was declared.

That's the "implicit MX rule" which I mean to deprecate.

| More importantly though are bounce messages from domains 
| without any SPF, since it may be an outbound only MTA, ie A 
| record matching HELO, but no matching MX or SPF. 

Bounce messages will have MAIL FROM:<>, so this scenario is
not a concern.

My reasoning for this, was that for a bounce the HELO is used 
to provide the domain for the SPF check (as long is it is a 
resolving FQDN), and your proposed rule would be part of the 
SPF checks (I assune)

Regards
Karl Prince


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