If you are running Kerio Connect, the admin interface allows you to generate a CSR and import a signed cert, but you need to do something a little funky if you use a provider that issues an intermediate certificate as well. Kerio details it here but you have to combine the intermediate cert with the server cert in the same .crt file.
Here is the Kerio Connect admin interface around SSL certificates:
After generating a .CSR under the “New” menu, and getting your signed cert back DigiCert also gives you their intermediate .crt. Pop-open both .crts you get back and paste the intermediate below the specific server cert. Here is my combo in TextWrangler. You need the BEGIN and END for each.
The new combination .crt you save this out to is the one you import into the Kerio Connect interface.