Exchange 2010 server cannot send to a specific domain

I manage a 2010 Exchange Server that has developed a problem.  The server cannot connect to a specific domain to send email.  The other domain can send to us. This seems to only effect a single domain.

I am struggling to understand the detail of the problem.  Changing the logging to verbose has these error
452 4.3.1 Insufficient system resources,
503 5.5.2 Need mail command,

I understand that this points to back pressure but I cannot see any stress on the server.

I cannot seem to identify it the error is with my server and isp internet problem or an issue with the other domain
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Both of these errors first seem to point at the server's system disk possible filling up:

From Microsoft's Technet  (

Send hello first
A generic SMTP error occurs when SMTP commands are sent out of sequence. For example, a server attempts to send an AUTH (authorization) command before identifying itself with an EHLO command.
It is possible that this error can also occur when the system disk is full.

Insufficient system resources
An out-of-memory error occurred. A resource problem, such as a full disk, can cause this problem.
Instead of getting a disk full error, you might be getting an out-of- memory error.
Ensure that your Exchange server has enough disk storage

Make sure that both your server's system disk and mailbox storage disk(s) have ample free space on them.  I believe if the system disk gets below a percentage of free space SMTP starts to have problems.

Now if this truly is happening to just one domain, then it may also be wise to contact the Admin of the other domain to see if they are getting any errors when you try to send.

What do your messsage tracking logs in Exchange say?  Have you tried to telnet to port 25 of the other mail server (the one you are sending to) and tried to send an email manually? (  Do this from the Exchange server.  You may need to download Putty or a similar program to allow the use of telnet (

Let us know what the results are of the above.
philblackburnAuthor Commented:
The server has 80gb of free disk space, I have none of the 1500x error I would expect to see in the event logs.

Most of the time the memory is fully used but the processes are idle.

The other domain can send to our domain.

When running telnet commands I get the same results as the send connector logs
If you get the errors when you try to send to them via an SMTP session, then I am willing to bet a few dollars that the problem is on the receiving domain and not on yours.  Since you used a telnet session you bypassed Exchange and SMTP on your system all together.  This means that it is likely their server that is having the problems and not yours.

Unfortunately it may be difficult to track that down.  A couple additional items to try:

1. Send an email from Gmail to the problematic domain and see if it goes through.
2. Go the and in the box type blacklist:youripaddress (ex. blacklist:  For this use the external IP Address your server would be sending from.  See if it comes back showing you on any blacklists.

It is most likely that either the remote server is having an internal systems issue -OR- for some reason it is rejecting mail from your server and those are the errors it is programmed to give you rather than the standard 5.5.X messages you would expect to see.

Best next bet would be to call the other domain's admin and explain that you have trouble sending and have tried via telnet and get the same results.

Let me know what you find out.
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philblackburnAuthor Commented:
I can send from Gmail to the domain
I do monitor Blacklists and we are clean.

From the logs I can see that it uses the extended smpt command set eg elho and my server uses helo could this be an issue?  Just a line of thought!
I don't *think* so or I would imagine you would see the problem a lot more often on other servers.  I would reach out the mail admin of the other system (if possible) and see if they show something on their side.  The bottom line is their server is throwing these messages, not yours.

My money is still on their system rejecting your domain for some reason or another.  I have just seen it too often.  If you try the SMTP from Telnet method and use a different domain name, does it fail the same way?

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You can also try using your domain name via the SMTP test method from a different IP address to see if it is related to your servers IP address.
You can also try using your domain name via the telnet to the SMTP server test method from a different IP address to see if it is related to your servers IP address.
philblackburnAuthor Commented:
I probably had all the answer just great to get a little more input
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