How do I encrypt emails sent from my server?

I seemed to find a solution for this at https://www.digitalocean.com/community/tutorials/how-to-install-and-configure-postfix-as-a-send-only-smtp-server-on-ubuntu-16-04#step-3-—-testing-the-smtp-server in the comment section by the user kevinruffus

He’s comment that solved my problem:

In addition to the instructions above, create your own self-signed certs, use LetsEncrypt, or use purchased certificates/keys (make sure you use wildcard or certificates specific to your hostname/FQDN), and edit main.cf to include:

# TLS parameters
smtpd_tls_cert_file=/etc/ssl/certs/fullchain.pem (change to suit your system)
smtpd_tls_key_file=/etc/ssl/private/privkey.pem (change to suit your system)
smtp_use_tls=yes
smtpd_tls_session_cache_database = btree:${data_directory}/smtpd_scache
smtp_tls_session_cache_database = btree:${data_directory}/smtp_scache

smtpd_tls_CAfile=(if your cert and CAfile aren’t rolled into a single file) It cleared the warnings from the emails for me, and shows TLS was used.

Edit: Corrected to show smtp_use_tls=yes, not smtpd_use_tls=yes

Same thing here, had to change from

smtpd_use_tls=yes

to

smtp_use_tls=yes

Don’t forget to

service postfix restart

Thx @andersdk ! I was having problems with smtpd_use_tls=yes ! and it was smtp_use_tls=yes as you correctly highlighted. Best regards.