There are two ways to access webmail. If the first technique doesn’t work, try the second.
If you get a security warning from your browser, it’s okay to continue. We are using only self signed ssl certificate on the server. cPanel use a type of certificate known as a self-signed certificate. Self-signed certificates work exactly like a certificate purchased through an SSL Certificate Authority, except that they are NOT signed by a Certificate Authority. Instead they are signed by our server; hence the term “self-signed”. That is the only difference. Apart from that, the encrypted connection using a self-signed certificate is as secure as any other SSL connection. Browsers assume that a site that uses an ssl certificate that has been verified by a certificate authority is safer than a site that does not. That is why you are getting the warning while accessing whm,cpanel,webmail,etc. You can safely ignore this warning and proceed further.