mail is on hermes. SSH to one of the mail domains (e.g. mail.earthclick.net)

Next, display a list of certificates

sudo certbot certificates

Where is it pointing?

sudo postconf smtpd_tls_cert_file smtpd_tls_key_file smtpd_tls_chain_files

smtpd_tls_cert_file = /etc/letsencrypt/live/mail.pdss.com/fullchain.pem
smtpd_tls_key_file = /etc/letsencrypt/live/mail.pdss.com/privkey.pem
smtpd_tls_chain_files =
postconf: warning: /etc/postfix/main.cf: support for parameter "smtpd_use_tls" will be removed; instead, specify "smtpd_tls_security_level"