RE: Multiple MX Records

  • From: "John Tolmachoff \(Lists\)" <johnlist@xxxxxxxxxxxxxxxxxxx>
  • To: "'[ExchangeList]'" <exchangelist@xxxxxxxxxxxxx>
  • Date: Thu, 18 Dec 2003 08:37:48 -0800

The problem is all on the receiving end. By starting a session and returning
a 421 code, they are telling your server to try again later. Your server is
doing exactly what it was told to do. There is no reason for your server to
try the other MX records. BTW, the following information is available at



    4.X.X   Persistent Transient Failure
       A persistent transient failure is one in which the message as
       sent is valid, but some temporary event prevents the successful
       sending of the message.  Sending in the future may be successful.



       X.2.X   Mailbox Status
          Mailbox status indicates that something having to do with the
          mailbox has cause this DSN.  Mailbox issues are assumed to be
          under the general control of the recipient.



       X.2.1   Mailbox disabled, not accepting messages
          The mailbox exists, but is not accepting messages.  This may
          be a permanent error if the mailbox will never be re-enabled
          or a transient error if the mailbox is only temporarily



John Tolmachoff


eServices For You


-----Original Message-----
From: paul_lemonidis@xxxxxxxxxxx [mailto:paul_lemonidis@xxxxxxxxxxx] 
Sent: Thursday, December 18, 2003 5:31 AM
To: [ExchangeList]
Subject: [exchangelist] Multiple MX Records

Hi All


Has anyone else come across this one? I have outbound messages queued up for
domains where there primary server is down. These queue up and are not
delivered which would seem fair enough on the face of it. Just one problem
the destination system has multiple MX records and the other hosts are up.
Why does Exchange refuse to use them? Even if I force the connection they do
not leave? Eventually they go of their own accord but this takes several
minutes or even hours? I cannot say at this stage if this is as a result of
the primary server coming back on line. I suspect it is.


> server
Default Server:


> set q=mx


Non-authoritative answer:     MX preference = 10, mail exchanger =
.net     MX preference = 20, mail exchanger =     MX preference = 30, mail exchanger =     nameserver =     nameserver =     nameserver = internet address = internet address = internet address =


I can telnet the second server just fine. The first one drops the connection
almost immediately. I suspect that is the answer? I am guessing that since
it does make a connection of sorts, albeit very briefly, it never tries the
second record as it thinks it is connected and thus never checks the other
MX records.


Above and below are relevant screen shots.


421 SMTP service not available, closing transmission channel


Connection to host lost.


Can someone tell me if I am correct and if there is any way around this
please. I know that strictly speaking, if my theory is correct, it could be
classed as a firewall issue at the remote end but that doesn't help me
deliver mail. The only short term way I see around this is to set up an
extra Virtual SMTP server and restrict the address space to just that domain
and forward to the second record host explicitly rather than using DNS.
Although that won't help with the trapped messages I suspect?


Any ideas, comments or suggestions please?


Many thanks in advance,




Paul Lemonidis. 

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