Multiple PTR records

Matus UHLAR - fantomas uhlar at
Fri Jan 16 18:40:28 UTC 2009

> On Jan 16, 2009, at 7:13 AM, Matus UHLAR - fantomas wrote:
> >Actually, it doesn't matter which PTR record will remain, unless there
> >will be any SPF record pointing to it.

On 16.01.09 10:12, Chris Buxton wrote:
> That is a common misconception.

No, it is not.

> I have seen mail bounced because of a  
> mismatch between SMTP greeting name and PTR record name. It's not as  
> common as the simple "is there any PTR record" check, but it does  
> happen.

- it's clear violation of RFC 5321 (and former 2821, 821) - server MUST NOT
  reject connection because of that. 
- some (many?,most?) SMTP clients can resolve their local address and use it
  as HELO string.

> The SMTP greeting name should also have an A record that resolves back  
> to the address used as the source address of the connection. 

There's "should" contrary to "MUST NOT" RFC section...

> I once  
> saw an SMTP server used to send mail from several unrelated domains,  
> where each one was sent out through a different address. The mail  
> server used the same name in the SMTP greeting regardless of which  
> domain it was sending for, and this caused problems for all of the  
> other domains.

This doesn't say anything about the source of the problem. 

If someone does not follow RFC's, I don't think we should "fix" the problem
on our side. 

And, again - it does not matter which PTR record will be left. But it must
point to hame that points back to the IP. And of course, if you send mail,
your MTA should be smart enough (or configured) to know what to use in HELO.

Matus UHLAR - fantomas, uhlar at ;
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