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>From <a class="moz-txt-link-freetext" href="http://www.zvon.org/tmRFC/RFC2821/Output/chapter5.html">http://www.zvon.org/tmRFC/RFC2821/Output/chapter5.html</a><br>
<br>
Once an SMTP client lexically identifies a domain to which mail will be
delivered for processing (as described in sections 3.6 and 3.7), a DNS
lookup MUST be performed to resolve the domain name [<a
href="http://www.zvon.org/tmRFC/RFC2821/Output/chapter9.html#22"
title="Mockapetris, P., "Domain names - implementation and specification", STD 13, RFC 1035, November 1987. Mockapetris, P., "Domain names - concepts and facilities", STD 13, RFC 1034, November 1987.">22</a>].
The names are expected to be fully-qualified domain names (FQDNs):
mechanisms for inferring FQDNs from partial names or local aliases are
outside of this specification and, due to a history of problems, are
generally discouraged. The lookup first attempts to locate an MX record
associated with the name. If a CNAME record is found instead, the
resulting name is processed as if it were the initial name. 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. If one or more MX RRs are found for a given name, SMTP
systems MUST NOT utilize any A RRs associated with that name unless
they are located using the MX RRs; the "implicit MX" rule above applies
only if there are no MX records present. If MX records are present, but
none of them are usable, this situation MUST be reported as an error.<br>
<br>
So, if you have no MX records, the MTA is supposed to check for an A
record and send it to the resulting IP address. If you have MX
records, they better be able to accept your mail or the message will
get bounced.<br>
<br>
--[Lance]<br>
<br>
<br>
Jon Carnes wrote:<br>
<blockquote type="cite" cite="mid1061562028.2615.14.camel@Anncons4">
<pre wrap="">You are correct that a machine does not need an MX record to receive
mail sent to that machine; however, since Ryan's server is attempting to
send his local mail off of the machine (rather than accept it locally)
there is clearly a problem of some sort.
In my dealing with folks on the mailman list, a common problem is that
they *have* mx records, and they are set incorrectly.
So if you have a suggestion that might help Ryan, lets hear it.
Jon Carnes
On Fri, 2003-08-22 at 09:30, Christopher L Merrill wrote:
</pre>
<blockquote type="cite">
<pre wrap=""><a class="moz-txt-link-abbreviated" href="mailto:rasch@raschnet.com">rasch@raschnet.com</a> wrote:
</pre>
<blockquote type="cite">
<pre wrap="">Some MTA's won't deliver to a domain without an MX. Why not have one?
</pre>
</blockquote>
<pre wrap="">Really? Which ones?
According to dyndns.org:
</pre>
<blockquote type="cite">
<pre wrap="">Many people think that you need an MX record to receive mail. This is incorrect.
In the absence of an MX, mail to a machine (for example, mail to
@who-needs-an-mx.dyndns.org or @yourcustomdns.com) will be handled by that
machine (in the case of my example, the machine at who-needs-an-mx.dyndns.org
or at yourcustomdns.com). This is the behavior that most people running mail
servers on their home machines want. For this reason, we do not recommend that
users wanting a basic mail configuration set up an MX. It is not necessary, and
it is possible to make mistakes in the MX record that will cause mail to end up
somewhere else.
</pre>
</blockquote>
<pre wrap="">Who's right?
C
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</pre>
</blockquote>
<pre wrap=""><!---->
</pre>
</blockquote>
<br>
<pre cols="72" class="moz-signature">--
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