An SMTP protocol error occurred

In the exchange system manager, under queue i see some mails are in queue and under additional queue information, i see the error An SMTP protocol error occurred. This error is only for (bellsouth.net) domain .
I'm running exchange server 2003 on windows 2003 std.
smdockeryAsked:
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Matthew MillersCommented:
You may need to add a reverse lookup in external DNS for your mail server.
When you send a message, do you get a NDR?
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smdockeryAuthor Commented:
We have a  reverse lookup in external DNS for your mail server

Reporting-MTA: dns;mailcss.CSS.IHR.COM

Final-Recipient: rfc822;franshim@bellsouth.net
Action: delayed
Status: 4.4.7
Will-Retry-Until: Wed, 23 Jan 2008 20:18:49 -0500
X-Display-Name: Frances McFarlane


Final-Recipient: rfc822;libido@bellsouth.net
Action: delayed
Status: 4.4.7
Will-Retry-Until: Wed, 23 Jan 2008 20:18:49 -0500
X-Display-Name: 'Libido Mail'
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Matthew MillersCommented:
Hmmm...is it just me, I cannot even telnet to either of the MX below, this would explain the delay notification. How are you relaying mail, direct to remote MX using DNS or via a smarthost?

If you relay direct, could you try and telnet to the MX below from your exchange server? Also do a NSLOOKUP and see if you get the same MX (nslookup -type=mx bellsouth.net)

> bellsouth.net

Non-authoritative answer:
bellsouth.net   MX preference = 10, mail exchanger = gateway-f2.isp.att.net
bellsouth.net   MX preference = 10, mail exchanger = gateway-f1.isp.att.net

gateway-f1.isp.att.net  internet address = 204.127.217.16
gateway-f2.isp.att.net  internet address = 207.115.11.16


C:\>telnet gateway-f2.isp.att.net 25
Connecting To gateway-f2.isp.att.net...Could not open connection to the host, on
 port 25: Connect failed

C:\>telnet gateway-f1.isp.att.net 25
Connecting To gateway-f1.isp.att.net...Could not open connection to the host, on
 port 25: Connect failed
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smdockeryAuthor Commented:
Yes we relay direct,

C:\>nslookup -q=mx bellsouth.net
Server:  css02.css.ihr.com
Address:  192.168.103.10

Non-authoritative answer:
bellsouth.net   MX preference = 10, mail exchanger = gateway-f2.isp.att.net
bellsouth.net   MX preference = 10, mail exchanger = gateway-f1.isp.att.net

gateway-f2.isp.att.net  internet address = 207.115.11.16
gateway-f1.isp.att.net  internet address = 204.127.217.16

C:\>telnet mail.bellsouth.net 25
Connecting To mail.bellsouth.net...Could not open connection to the host, on por
t 25: Connect failed

C:\>


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Matthew MillersCommented:
I think there is a problem with the MX (both) for that domain, i have tried at a couple of customer sites with the same outcome.

I am not from the US, but i would have thought bellsouth are quite big?? You may want to give them a bell (hehe) and see if they are having problems.

In the end, this is not really your issue.
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smdockeryAuthor Commented:
Do you have a number I call ???
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Matthew MillersCommented:
No idea, www.bellsouth.net and have a look.
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