postfix-users

Re: dns A records not used when there's no MX

Subject: Re: dns A records not used when there's no MX
From: wietse AT porcupine DOT org (Wietse Venema)
To: Carlos Carvalho <carlos AT fisica.ufpr DOT br>
Date: Fri, 10 Aug 2007 20:55:16 -0400 (EDT)
Carlos Carvalho:
> Messages have been getting stuck in the smtp queue because the
> destination doesn't have a MX record. Here's an example:
> 
> Aug  9 07:49:34 hoggar postfix/smtp[7034]: 3B95232E1A4: to=<X AT example DOT 
> com>, relay=none, delay=80142, delays=80142/0.02/0/0, dsn=4.4.3, 
> status=deferred (Host or domain name not found. Name service error for 
> name=example.com type=MX: Host not found, try again)
>
> The dns answer is "MX record currently not present".

No that was NOT the DNS reply. "Host not found, try again" means
that no valid reply was received.

        Wietse

> The messages stay
> in the queue until the maximal_queue_lifetime expires. However the
> example.com destination *does have* an A record. According to rfc 2881:
> 
>    "If no MX records are found, but an A RR is found, the A RR is
>    treated as if it was associated with an implicit MX RR, with a
>    preference of 0, pointing to that host."
> 
> So why are the msgs not being sent to the IP address pointed to by the
> A record? I have ignore_mx_lookup_error=no and
> smtp_defer_if_no_mx_address_found=no (default values), with postfix
> version 2.4.3.
> 
> 


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