Exchange 2010 server not accepting inbound SMTP connections

One of our exchange servers has stopped accepting inbound SMTP connections.
I have tried telneting to the offending server, running netstat -aon |find ":25 "  shows the connection as SYN_RECEIVED which is as far as it gets.
comparing the receive connector against the working server show no differences, disk space is fine and mail is being delivered from the working server.

Can anyone advise ?
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Jose Gabriel Ortega CastroCEOCommented:
Check exchange services,
if they are running, restart mailbox transport and information store. (assuming 2013/2016). Maybe an exchange reboot?
Describe a bit better your infrastructure, please. We know that you have several serves but not how many exactly, if you have dags or not, etc.

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AmitIT ArchitectCommented:
Any firewall or antivirus? Try to bypass or disable it and test again. Also, did you restarted the server and checked if all services are up. Finally, check for errors in application.
AndyNunnAuthor Commented:
Thanks for the suggestions guys,
We have 2 server 2008 R2 boxes running Exchange 2010, with a single DAG,  patches up to date as of 2 weeks ago.
Both boxes have been restarted and all relevant exchange services are running
have disabled AV - webroot  and still only get SYN_RECEIVED, nothing written to the event logs at the time i try telnet
If it's a DAG, I assume you have configured both servers with SMTP connector to accept incoming email.

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Should provide all the receive connectors configured in the environment.

Set-ReceiveConnector "OffendingServerSMTPReceiveConnector" -ProtocolLoggingLevel Verbose

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Should set the logging to verbose, next you can access the logs at the following default location:
C:\Program Files\Microsoft\Exchange Server\V14\TransportRoles\Logs\ProtocolLog
Jose Gabriel Ortega CastroCEOCommented:
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