The difference between our Squirrel Signing Authority and Verisign or other commercial certificate signing authorities is the source.
We have our own root certificate for Squirrel Signing Authority that you should install in your browser using the instructions on this page.
Once this certificate has been installed it will authenticate all certificates on our servers. If any of the server certificates are invalid or change, the browser will detect it. If the server certificate is compromised, it will not be signed by the installed "Squirrel Signing Authority" certificate anymore, and your browser will detect the problem.
Root Certificates like the Squirrel Signing Authority root certificate are used to verify the certificates for web sites. The private version of the root certificate is used to sign all certificates issued to our secure sites.
The key to encryption is, without that private root certificate, no one can create fake certificates on our site that will be seen as signed by our official root certificate. The public version of this root certificate is the file ca.crt that you download by clicking on the "CLICK FOR CERT" in order to install it in your browser.
This file can only be used for determining if a web site's certificate was signed by our root certificate. It is not possible to use this "public key" to sign a certificate with the purpose of impersonating our servers. The web site's certificates are also used to encrypt any data transferred between you and them, so all of your email is secure.
Please follow your device (phone, tablet etc.) and software (Outlook, Thunderbird etc.)providors instructions for accepting certificates for sending and recieveing email securely.