Setup certbot

Check the services running on the host:

nmap $DIGITALOCEAN
21/tcp  open   ftp
25/tcp  open   smtp
80/tcp  open   http
143/tcp open   imap
443/tcp open   https
465/tcp closed smtps
587/tcp open   submission
993/tcp open   imaps

"Certbot could not find a VirtualHost for mail.vasilian.net in the Apache configuration.
Please create a VirtualHost with a ServerName matching mail.vasilian.net and try again."

Read about installing the Let's Encrypt Certbot and how to create a SSL certificate for the domain and subdomains.

dnf install certbot python3-certbot-apache
certbot --apache

This will detect only the www and domain name, but will not show the mail. subdomain

You have to re-run with expand option to include also the mail.vasilian.net

certbot --expand -d www.vasilian.net,vasilian.net,mail.vasilian.net

Select this option when asked:

We were unable to find a vhost with a ServerName or Address of mail.vasilian.net.
Which virtual host would you like to choose?
- - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - -
1: ssl.conf                       |                       | HTTPS | Enabled
2: vasilian.net.conf              | Multiple Names        |       | Enabled
3: vasilian.net-le-ssl.conf       | Multiple Names        | HTTPS | Enabled

To check if SSL certificate is installed correctly use the SSL Server Test page.

Add a crontab job to renew the certificate.
Use -e option to edit (vi) /var/spool/cron/root

crontab -e

# insert next line, save & exit
* * * * 1 certbot renew >/dev/null 2>&1

To list all crontab jobs

crontab -l
* * * * 1 certbot renew >/dev/null 2>&1

crontab -u mihai -l
no crontab for mihai

To check a simple command use Crontab Generator