How to secure mail server with Let's Encrypt certificate?
In order to secure mail server using a certificate from Let's Encrypt use a certificate issued to a corresponding hostname. For that:
- Create a corresponding domain with the hostname of the server (example.com) in Plesk.
- Go to Domains > example.com > Let's Encrypt and install Let's Encrypt certificate for the domain.
- After that, you can use installed certificate to secure Plesk or mail server under Tools & Settings > SSL/TLS Certificates > Certificate for securing mail section > Change (button).