Certificate issue.

To request a certificate reissue from a certificate authority (CA), you typically need to create a certificate renewal request and submit it to the CA. Here are the general steps you can follow:

1. Create a Certificate Renewal Request: You can do this through the Exchange Admin Center (EAC) or using the Exchange Management Shell.
   • In the EAC, navigate to Servers > Certificates, select the server holding the certificate, and click on the Renew link for the relevant certificate.
   • If using the Exchange Management Shell, you can generate a renewal request using the Get-ExchangeCertificate command.
2. Submit the Request: After creating the renewal request, you will need to send it to the CA. This can be done through the CA's web interface or via email, depending on the CA's process.
3. Receive the New Certificate: Once the CA processes your request, they will issue a new certificate, which you will need to install on your server.
4. Install the Certificate: Follow the instructions to install the new certificate on your server to ensure it is recognized and used correctly.

Make sure to check the specific instructions provided by your CA, as the process may vary slightly depending on whether you are using an internal CA or a commercial CA.