Install certificate in two steps.
Step I - import Intermediate Certificate(s)
Copy intermediate SSL certificate and paste it to text editor document. Save it as intermediate.cer.
Open Microsoft Management Console.
Go through options: File, Add/Remove Snap In, Add, Certificates and Add again.
New window will appear. Select Computer Account option and click Next. Choose options: Local Computer, Finish, Close and OK.
Now choose Certificates and Intermediate Certification Authorities.
Right click on Certificates and choose options: All Tasks and Import.
Wizard will start - follow all instructions till the end - it will add intermediate certificate. Close the console.
Step II - import SSL Certificate
Copy SSL certificate and paste it to text editor document. Save it as YourDomain.cer.
Open Exchange Management Shell and use the command: Import-ExchangeCertificate -Path C:\YourDomain.cer
Enable-ExchangeCertificate -Services "SMTP, IMAP, POP, IIS" Note: Path and file name (YourDomain.cer) must be accurate to yours.
To verify that your certificate is running and enabled run the following command: Get-ExchangeCertificate -DomainName server.domain.com
In response thumbprint, an abbreviated list of the services and YourDomain.cer will display.
If certificate does not run properly, use a command: Enable-ExchangeCertificate -Thumbprint [paste here] -Services "SMTP,IMAP, POP, IIS"
Reboot your server and test your certificate.
Important: Do not use the Certificate snap-in to import the certificates for any service on an Exchange server. Using the Certificate snap-in to import certificates on Exchange servers will fail. Therefore, TLS or other Exchange certificate services will not work.