The Plesk admin area is secured by an SSL based connection (HTTPS) and out of the box uses a self-signed certificate. This will generate a warning in most browsers, stating that the certificate can't be verified. While this doesn't present a security risk, it can be disconcerting to some clients. You can purchase an SSL certificate for your plesk domain (eg admin.yourdomainname.com.au) or use the latest Plesk Let's Encrypt extension to secure it for free.
You will need to have Let's Encrypt Plesk extension installed on your Plesk server. If you do not have it installed follow this link on How to install Let's Encrypt on Plesk.
- Login to your Plesk server as the admin user.
- Add either a subdomain (see How to Add a Sub Domain in Plesk) if you have the root level domain pointed at your server (eg yourdomain.com.au) or add a new domain in with the full hostname of the server (ie admin.yourdomainname.com.au).
- Select your subdomain or website, then click on Lets Encrypt:
- Select "Use this certificate to secure connections to Plesk":
- Then, click on Install:
This will contact LetsEncyrpt, generate the certificate and then install it for you.
- Got to your Plesk server URL in your browser. It should now show a green lock to indicate that the certificate is now valid.