Check Mail-Certificate

If you use letsencrypt certificates you will have to renew them manually (or create some cronjob for this). With the following command you can test your certificate and check the expiration date.

Just replace in the following command with your own host and run it:

printf 'quit\n' | openssl s_client -connect -starttls smtp | openssl x509 -enddate -noout

The IMAP specific command looks slightly different:

printf 'quit\n' | openssl s_client -connect -starttls imap | openssl x509 -noout -dates