Hello All,

I have Exchange 2007 running on Windows 2008. There are two servers, one is hub and cas and another one is mail box.

Last two days the mails are not sending from the server, it is in the queue.

Space is available, Send connector is configured. And I don't see any error message.

I am able to receive the mails.

Can someone help me to solve this issue?

Thanks in advance

Tonio

Hello Tonio,

Have you checked the queueof first server? You can see, by what error the messages are stuck.

Check the event vieweralso and see there are some error related toActive directory, dnsetc. Mostly, it can be related to DNS

Hello

tip: check send conector logs for error. and on queue last error message

Hello Manu,

I had an image of my AD and restored. But still facing the same problem. If DNS is the problem, I will not be able to receive the mails. Not sure, only my doubt.

Thanks

Tonio

Hello,

Thank you for your reply. Please find the error message given below.

Delivery is delayed to these recipients or distribution lists:

This message has not yet been delivered. Microsoft Exchange will continue to try delivering the message on your behalf. 

Thanks

Tonio

Tonio,

It can't be say, how the DNS issues affects. Better, you verify event viewer for any issues.

Also, look in to the Queue (as I mentioned in my last post) and understand what error message you have seen there.

As Sneff_Gabor mentioned, checking the connector logs will also help

Hello Manu,

Thank you so much for the reply.

Here is the log file

#Software: Microsoft Exchange Server
#Version: 8.0.0.0
#Log-type: SMTP Send Protocol Log
#Date: 2015-07-09T07:01:22.357Z
#Fields: date-time,connector-id,session-id,sequence-number,local-endpoint,remote-endpoint,event,data,context
2015-07-09T07:01:22.357Z,Smtp Send Connector,08D288139CE8E5B2,0,,2404:6800:4003:c00::1b:25,*,,attempting to connect
2015-07-09T07:01:22.357Z,Smtp Send Connector,08D288139CE8E5B2,1,,2404:6800:4003:c00::1b:25,*,,"Failed to connect. Error Code: 10051, Error Message: A socket operation was attempted to an unreachable network 2404:6800:4003:c00::1b:25"
2015-07-09T07:01:22.357Z,Smtp Send Connector,08D288139CE8E5B2,0,,74.125.200.27:25,*,,attempting to connect
2015-07-09T07:01:22.357Z,Smtp Send Connector,08D288139CE8E5B2,1,192.168.2.12:24478,74.125.200.27:25,+,,
2015-07-09T07:01:22.528Z,Smtp Send Connector,08D288139CE8E5AD,0,,2404:6800:4003:c00::1b:25,*,,attempting to connect
2015-07-09T07:01:22.528Z,Smtp Send Connector,08D288139CE8E5AD,1,,2404:6800:4003:c00::1b:25,*,,"Failed to connect. Error Code: 10051, Error Message: A socket operation was attempted to an unreachable network 2404:6800:4003:c00::1b:25"
2015-07-09T07:01:22.528Z,Smtp Send Connector,08D288139CE8E5AD,0,,74.125.200.27:25,*,,attempting to connect
2015-07-09T07:01:22.528Z,Smtp Send Connector,08D288139CE8E5AD,1,192.168.2.12:24480,74.125.200.27:25,+,,
2015-07-09T07:01:26.091Z,Smtp Send Connector,08D288139CE8E5F2,0,,195.74.38.202:25,*,,attempting to connect

from your log it says unable to connect on port 25.

check the services of your servers, also verify telnet servername 25 whether it is responding to command. try restarting the services

Hi,

Check with the ISP, if they have recent changes in accessing port 25.

Hello Manu,

I would like to change SMTP 25 port number to 587. Where can I change the port number in exchange 2007?

Thanks in advance

Tonio

Hi Tonio,

TCP Port 25 is the default port used for message transmission between SMTP servers, we can modify the port in Send Connector, please refer to: https://technet.microsoft.com/en-us/library/bb629503(v=exchg.141).aspx#Shell

It's not recommend change this port, it also inbound and outbound mailflow, for your reference: https://technet.microsoft.com/en-us/library/bb331973(v=exchg.150).aspx

For your question, do you have deploy firewall or TMG in your environment? If so, please ensure the 25 port is available. You can use telnet to test SMTP communication, please refer to: https://support.microsoft.com/en-us/kb/153119