RE: Multiple MX Records

  • From: "Mulnick, Al" <Al.Mulnick@xxxxxxxxxx>
  • To: "'[ExchangeList]'" <exchangelist@xxxxxxxxxxxxx>
  • Date: Thu, 18 Dec 2003 08:51:35 -0500

If I recall correctly, there was an issue similar to this that was fixed in
later releases.  The problem was with the underlying SMTP (I think; it's
been some time).  What versions of OS and app are you running? 
The issue was something to do with the way the SMTP service would use MX
records.  It was very similar to what you describe.


From: paul_lemonidis@xxxxxxxxxxx [mailto:paul_lemonidis@xxxxxxxxxxx] 
Sent: Thursday, December 18, 2003 8:31 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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