Will existing domains be secured if Keep website secured with free SSL/TLS certificate option is enabled in Service Plan?

Question

Will an already existing domain have a free Let's Encrypt certificate installed when extensions are configured as follows on the service plan level? 

Keep websites secured with free SSL Certificate is enabled in Plesk > Service Plans > example_plan > Additional Services:

• With SSLit! extension:
• With Let's Encrypt extension:

Answer

Option secures both newly created domains and existing ones by execution of the scheduled task configured in   Plesk > Tools & Settings > Scheduled Tasks :

• With SSLIt! extension:

  PLESK_INFO: /opt/psa/admin/bin/php -dauto_prepend_file=sdk.php '/opt/psa/admin/plib/modules/sslit/scripts/keep-secured.php'

• With Let's Encrypt extension:

  PLESK_INFO: /opt/psa/admin/bin/php -dauto_prepend_file=sdk.php '/opt/psa/admin/plib/modules/letsencrypt/scripts/keep-secured.php'

It runs every hour and checks if a domain has an SSL certificate. Hence, if certificate installation fails, it will try to install it in one hour.