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External clients can't send emails through POP3/SMTP hosted on our SBS2011

Posted on 2016-09-08
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Last Modified: 2016-10-04
We have an SBS 2011 server running Exchange which we have enabled POP3 access on. A branch office has 4 PC's that use Outlook and all connect to the POP3 boxes using incoming and outgoing server address remote.ourclient.com.  Incoming email works fine but they suddenly cannot send emails.  I've set up a test connection in my office and we can't send either so we know it's not an issue with their network.  Their ability to send seems to have stopped around the same time we had some issues with the firewall and the SBS server which resulted in us having to restart he firewall and run the "Connect to Network" wizard on the SBS server.  Normal Exchange users are able to send and receive OK but something seems to have broken on either the SBS server or the Watchguard firewall.  I've checked and there is a firewall policy for port 587 pointing to the SBS server and the outgoing port on the Outlook clients is set to 587.  Could really use some urgent advice on what this could be please.  Many thanks
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Question by:Adam Lydiate
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by:John Hurst
ID: 41789390
See if you can track the traffic for one machine. Make sure you have Outgoing Authentication set and that you have the Port set for 587 / SSL or TLS.  If you set TLS try SSL to see.

Use the Outlook "test this account" and then copy the complete message and post it here.
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Expert Comment

by:Andy M
ID: 41789397
Have the Outlook clients got "Server requires authentication" enabled on the outgoing server connection settings?

Also check receive connectors in Exchange - I think it's the default client connector which should be set to accept on port 587 and allow access from all networks. If you have no receive connector set for this then it would not work.

What happens if you try to telnet on ports 25 or 587 from the affected machines and your internal network - do you get any response, does it let you send an email via telnet?
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Author Comment

by:Adam Lydiate
ID: 41789610
Tried telnet got "Could not open connection to the host on port 587: connect failed" tried again with 25 and that connects, but if I change the port to 25 in Outlook it still won't send
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by:John Hurst
ID: 41789619
There must be a firewall blockage for the issue above to appear.
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Assisted Solution

by:Andy M
Andy M earned 250 total points
ID: 41789840
I agree with John, there'll likely be  block on port 587 that needs sorting for the connection to happen.

Have  alook at your external firewall and get port 587 forwarded to your Exchange server, Also check the Exchange server itself - is Windows Firewall turned on, if so, has it got an exception for Port 587.

As for 25 - connection looks like but it may have a configuration somewhere that's preventing authenticated Exchange users from using it (likely be a setting in the receive connector - may be easier trying to address the port 587 issue first before messing with the Exchange setup).
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Author Comment

by:Adam Lydiate
ID: 41790842
HI thanks for your response, Checked the firewall and it's definitely forwarding 587 to the SBS server.  Have turned off Windows Server firewall altogether and still no joy.
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John Hurst earned 250 total points
ID: 41791082
Please post the entire Outlook error message here when you a Send / Receive test as we asked above.

Also, if you can, set up a laptop with very precisely the same Outlook settings. Test internally and post the error number. Then take the laptop to a different network and test on a different network.
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Author Closing Comment

by:Adam Lydiate
ID: 41827973
Thanks for your help guys.  I set it up locally and still didn't work.  Frustratingly the problem all along was that the user gave us the wrong password! Thanks for your help though.
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by:John Hurst
ID: 41827978
Thanks for the update and I was happy to help.
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