[Helper] Update expiry-dates.sh

- Use port numbers from `mailcow.conf` instead of fixed port numbers 
- reformat output

helper-scripts/expiry-dates.sh

@@ -3,10 +3,11 @@
 [[ -f mailcow.conf ]] && source mailcow.conf
 [[ -f ../mailcow.conf ]] && source ../mailcow.conf
 
-POSTFIX=$(echo | openssl s_client -connect ${MAILCOW_HOSTNAME}:25 -starttls smtp 2>/dev/null | openssl x509 -inform pem -noout -enddate | cut -d "=" -f 2)
-DOVECOT=$(echo | openssl s_client -connect ${MAILCOW_HOSTNAME}:143 -starttls imap 2>/dev/null | openssl x509 -inform pem -noout -enddate | cut -d "=" -f 2)
-NGINX=$(echo | openssl s_client -connect ${MAILCOW_HOSTNAME}:443 2>/dev/null | openssl x509 -inform pem -noout -enddate | cut -d "=" -f 2)
-echo TLS expiry dates:
-echo Postfix: ${POSTFIX}
-echo Dovecot: ${DOVECOT}
-echo Nginx: ${NGINX}
+POSTFIX=$(echo | openssl s_client -connect ${MAILCOW_HOSTNAME}:${SMTP_PORT} -starttls smtp 2>/dev/null | openssl x509 -inform pem -noout -enddate | cut -d "=" -f 2)
+DOVECOT=$(echo | openssl s_client -connect ${MAILCOW_HOSTNAME}:${IMAP_PORT} -starttls imap 2>/dev/null | openssl x509 -inform pem -noout -enddate | cut -d "=" -f 2)
+NGINX=$(echo | openssl s_client -connect ${MAILCOW_HOSTNAME}:${HTTPS_PORT} 2>/dev/null | openssl x509 -inform pem -noout -enddate | cut -d "=" -f 2)
+
+echo "TLS expiry dates:"
+echo "Postfix: ${POSTFIX}"
+echo "Dovecot: ${DOVECOT}"
+echo "Nginx:   ${NGINX}"