exchange emails being delayed

Posted on 2014-09-08
Last Modified: 2016-06-13
I have a problem where emails from my server are failing or being delayed, we are running exchange 2010, i'm not sure what the issue is, internal emails are fine and we are receiving ok.
I have run best practice and exchange mail flow trouble-shooter but still cannot find the issue?? I'm not sure what else I need to try??
Question by:pcspcs2011
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Expert Comment

ID: 40310309
Have you checked your Exchange Queues and seen the emails backing up? If so, what was the last error information? Do you use a smarthost or are you sending directly to the internet for delivery? If a smarthost, can you connect to the address using telnet over port 25. If you can do that what happens when you issue a helo command? You should be receiving something in your event logs. Can you share that as well?

Expert Comment

ID: 40310331
Also, check that your logs and mail data directories as well as your Hub transport server all have plenty of disk space. Low to no space can trigger back pressure and cause delivery failures/delays.

Author Comment

ID: 40311533
have checked exchange que and I am getting this message  451.4.4.0 DNS Query failed??

not sure where to go from here?

Expert Comment

ID: 40311659
So how does mail leaving your organization work? Do you send it to an appliance (SmartHost) or directly to the internet using MX records? You can find this by looking at your send connectors on your hub transports. If it is straight to the internet check the validity of your DNS settings and make sure your Exchange machine can get to the internet. If it is a smarthost make sure you can still get to the smarthost with telnet as I suggested earlier. Also, please let me know what you have done to try and resolve the issue so we are not repeating steps. Have you rebooted, restarted the DNS service, etc?

Accepted Solution

pcspcs2011 earned 0 total points
ID: 40354564
I have fixed the issue, someone in had installed some anti-malware software on the server, as soon as it was removed emails worked normally

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