Exchange 2016 – POP3 clients not connecting

 

Exchange 2016 POP3 clients not connecting. Here is my solution and I hope it helps resolve your problem with Exchange 2016 POP3 clients not connecting

So I ran into the following when trying to connect Exchange 2016 POP3 accounts. Does not matter what I did I kept running into the same issue with POP3 clients not connecting

Event log showed the following under the servers system log every time a POP3 connection was trying to get established:

EventID: 36888
Source: Schannel
General: A fatal alert was generated and sent to the remote endpoint. This may result in termination of the connection. The TLS protocol defined fatal error code is 10. The Windows SChannel error state is 10.

Event 36888 - Schannel - Exchange 2016 POP3 clients not connecting. Here is my solution and I hope it helps resolve your problem with Exchange 2016 POP3 clients not connecting

Exchange 2016 POP3 clients not connecting

SOLUTIONS

1. Open Exchange management shell as Administrator and run the following:

Get-PopSettings | Format-List

Here you need to ensure that a couple of things are correct:

1. ExternalConnectionSettings should have a value similar to the following:

{exchange.yourdomain.com:110:TLS, exchange.yourdomain.com:995:SSL}

If not run the following command to set it:

Set-PopSettings -ExternalConnectionSettings "exchange.yourdomain.com:995:SSL",
"exchange.yourdomain.com:110:TLS" -X509CertificateName exchange.iemas.co.za

Now run the following to restart the POP3 services

Restart-Service MSExchangePop3; Restart-Service MSEXchangePOP3BE

2. Ensure that EnableGSSAPIAndNTLMAuth is set to false

If not run the following command to set it:

Set-PopSettings -EnableGSSAPIAndNTLMAuth:$false

Now run the following to restart the POP3 services

Restart-Service MSExchangePop3; Restart-Service MSEXchangePOP3BE

3. Ensure that all exchange servers are using the same SSL certificate for the POP3 service
4. Try changing the service for POP3 to the default certificate generated during installation

Test POP3 connection and you should get a certificate error. Now you change it back and it should work again. Please let me know if this resolved your issue.

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