ECDSA prohibits using Let's Encrypt certificate to protect mail server

False mail security SSL certificate applied to .pem files while GUI displays correct selection​

Plesk 17.8, latest patches
CentOS 7.6​

Created a "Let's Encrypt" certificate for the host name. Made it "default" certificate. Then used this certificate to secure the Plesk website and mail service. The certificate files on are updated (verified by...​