Messages to some domains not sending (sitting in SMTP queue retrying but failing to deliver)

I have 3 Exchange 2k (sp3) boxes and 1 Exchange 2k3 (sp1) in my organistation.

2 of the 2k boxes are experiencing problems with outgoing mail (but only to some domains).  There is nothing in the event logs to suggest that there is a problem, however when looking at the queues on each I see many messages there in constant "retry" state, some of which have been like that for 24 hours.

users have been getting delivery notifications (delays) but it doesnt say what the problem is exactly

id be really greatful for any help!


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From your exchange server, open command prompt. Using nslookup, check mx records for troubled domains. For example, if troubled domain is, do following from nslookup
nslookup> set q=mx

Nslookup will respond with a bunch of mail exchanger records for domain. If it does not then you have DNS issue.
Assuming that you get mail exchanger records, exit from nslookup and open telnet session on port 25 to mail exchanger server with lowest preference.

>telnet 25

When you connect (assuming you can, otherwise it might be network issue) check what would be response from the other side. Often it will tell you when there is a problem. If you get prompted type "Helo" where "" is the name of your domain - and wait for response...
EffEffTeeAuthor Commented:
ok, so the MX record information is returned to me correctly, and I can telnet into the exchanger - although after the first line "220 ESMTP ; date time" any text I write doesnt show up...

However, if I type "helo" in and hit enter it responds with "250 Helo and their IP address".  Is that a normal response?
Yes, code 250 is a normail response.
After that you usually go like this:

>telnet 25
220 ESMTP ; date time"
250 Helo and their IP address"
mail from:
250 sender <> OK
rcpt to:
250 ...

BTW, do you have any Outlook 2007 clients in your organisation?


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EffEffTeeAuthor Commented:
if I go through that process and I find I can send mail (i.e. the problem is in Exchange itself) - what are the next steps?  Is there something I can look for in Exchange?

and nope, we don't have any 2007 clients...

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