Forum Discussion

Neymar's avatar
Neymar
Copper Contributor
Feb 12, 2026

Exchange 2019 Certificate Error

Hello guys,

I plan to migrate my users on Exchange 2019, currently, i have 2 Exchange 2013 servers. As soon as i installed the exchange Server 2019, I changed all the virtual directories and i also runned the command to make sure the users doesn't connect on the new server. But now every users who uses Microsoft Outlook from the environment have a pop up that says that the certificate is not valid, and its normal because I can't apply the services SMTP and IIS on my wildcard certificate.

 

Indeed, when i enable the services SMTP and IIS on my new certificate, it doesn't apply. I tried to enable from the ECP, it says "Are you sure you want to replace the existing certificate", when i say yes, it doesn't change anything, the smtp service is still unchecked.

 

I also tried to stop IIS and restart IIS, restart the server but it doesn't changed anything, and I also tried to enable the services directly with the powershell command with the correct thumbprint of the wildcard certificate as it is said on the event viewer :

"Enable-ExchangeCertificate -Server "EX01-2019" -Thumbprint A6BC992FDD... -Services SMTP,IMAP,IIS -Force"

But it still don't work, when i check the certificate, only the service IIS is active. I had to uninstall completely the exchange server, because users were complaining about the pop up.

Have anyone faced this problem before?

Thank you very much for your advices guys

2013
Exchange Server

3 Replies

  • AnnTaeYoun's avatar
    AnnTaeYoun
    MVP
    Feb 12, 2026

    Hello! Neymar​ 

    The certificate name mismatch occurs because the newly added Exchange Server 2019 is being accessed directly by users' Outlook clients.

    To resolve this issue, block inbound TCP port 443 traffic from client networks to the Exchange Server 2019 IP address at the firewall level.

    This will prevent direct client connections to the backend server and ensure that Outlook connects only through the designated load balancer or Client Access endpoint.

    • Neymar's avatar
      Neymar
      Copper Contributor
      Feb 13, 2026

      Hello AnnTaeYoun​ 

      Thanks for your answer, but even by doing this, the pop up that says that the certificate is not correct still appears.

    • Neymar's avatar
      Neymar
      Copper Contributor
      Feb 13, 2026

      Hello AnnTaeYoun​ 

      Thanks for your answer, but if I do this, as soon as I migrate my users on Exchange 2019, what will happen? I will have the same error i guess