Ems Smtp Configuration

I want to make a secure email connection with starttls for M365. I then created an M365 certificate with openssl. I followed this guide https://docs.fortinet.com/document/forticlient/7.4.1/ems-administration-guide/385506/configuring-smtp-server-settings. But I couldn't upload the certificate to Ems. Ems asks for a certificate password or private key, unfortunately I don't have one. How can I do this?