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I reinstalled an exchange server and now when outlook starts, it popup an mes
sage saying the certificate isn't trusted. What could be wrong? I have installed a correct certificate with right name on the server.
I already purchased a certificate from Network Solution so it is trusted. The cert I am talking about is the Microsoft Exchange Certificate (highlighted in Yellow). It is auto issued to local exchange server. 
Is this cert used by Exchange Backend IIS? Does it need to be installed Trusted Cert Store?
Hi @alan gao ,
Yes, by default this certificate should be used both frontend and backend. Also it will automatically installed in your Exchange server's trusted root.
Oh I guess you're using outlook from another computer not where Exchange installed right? Then you could also install this certificate to the root to avoid it.
Regards,
Lou
Hi @alan gao ,
Have you installed the certificate to the Trusted Root Certificate Auth？
You could click Install Certificate from the first picture and choose Local Machine then Browse the root.
Then restart IIS.
This may help you: How to use a internal Windows CA (Certificate Authority) in Windows 2012 with Exchange 2013
Please Note: Since the web site is not hosted by Microsoft, the link may change without notice. Microsoft does not guarantee the accuracy of this information.
Regards,
Lou
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the outlook is on anther computer other than where exchange is installed. There are thousand of clients outlook, I can't install it one by one for each and every PC. Is there a way to install it so very computer will trust it? It is in a domain enviroment.
Hi @alan gao ,
Then you should use the Business Certificate that you've paid for, since the self-signed certificates are not trusted by other clients.
You should Import or install a certificate on an Exchange server then Assign certificates to Exchange Server services. So Exchange will use this cert for authentication.
Also after this, check the IIS https bindings for both FrontEnd and BackEnd.
I have installed a business certificate and bind to the IIS service.
Hi @alan gao ,
Have you ever imported this certificate to Exchange and assigned services?
Only after you assigned services will Exchange use this certificate for it's functions.
Also please check if he certificate SAN has include your mailbox & CAS server and it should be used on both servers.
After assigned the certificate:
Regards,
Lou
Hi @alan gao ,
Do the suggestions above help? If the issue has been resolved, please click “Accept as answer” to mark helpful reply as an answer, this will make answer searching in the forum easier and be beneficial to other community members as well.
Regards,
Lou
If the response is helpful, please click "Accept Answer" and upvote it.
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