Hi Everyone,
Some of our users have been having trouble sending messages to the earthlink
domain. I contacted them and they replied that it could be an incorrect
configuration in my MTA:

" the mailserver which attempted to deliver mail to the earthlink.net e-mail
address was initially unable to successfully deliver the mail to the
earthlink.net MX (more than likely due to high load on our end; no EarthLink
MX host was available to accept the transaction at the moment of the
delivery attempt), and so the EarthLink 'A' record was attempted by the
sending mailserver.  The earthlink.net 'A' record, however, forwards port 25
connections to our outbound SMTP servers.  Unless the mailserver attempting
the transaction maintains IP connectivity through the EarthLink network,
delivery attempts through the 'A' record will consequently fail.

The behavior exhibited by the sending mailserver, in this case, is not
standard.  According to RFC 2821, "Address Resolution and Mail Handling":

  "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."

Currently the EarthLink.net mx record resolves as follows:

mx4.earthlink.net
mx5.earthlink.net
mx6.earthlink.net
mx7.earthlink.net
mx8.earthlink.net
mx9.earthlink.net
mxa.earthlink.net
mxb.earthlink.net
mxc.earthlink.net
mxd.earthlink.net
mxe.earthlink.net
mx1.earthlink.net
mx2.earthlink.net
mx3.earthlink.net


You may wish to verify that you are able to successfully resolve this record
through your nameservers, and that you can successfully route to these
hosts. 

Assuming that the earthlink.net MX is resolvable, however, our engineers
have informed us that if the sending mailserver cannot immediately establish
a connection to deliver the intended e-mail, the MTA should attempt to retry
a connection to the EarthLink MX, rather than defaulting to the
earthlink.net 'A' record or smtp.earthlink.net."

I can succesfully resolve these records through my nameserver, so my
question is what on my MTA would be incorrectly configured?

Thanks in advance for the help!!

Sean



~~~~~~~~~~~~~~~~~~~~~~ 
Sean Brandt, MCSE 
US Network Manager
Lonely Planet Publications, USA 
tel: 510.893.8556 x217 
mobile: 510.541.2601 
[EMAIL PROTECTED] 


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