If your received the following error after PGP Desktop installation, please check your mail client and disable SSL/TLS authentication.
Please Disable SSL/TLS in your email client so that PGP can secure your email as well as securing the connection via SSL/TLS
If you wish to use PGP Desktop for your email encryption, you need to disable SSL/TLS in your email client as PGP Desktop cannot process your email if it is already SSL/TLS encrypted. The PGP Messaging proxy sends the email from your email software to PGP Desktop for processing and then sends the email on to your email server; the PGP email proxy will automatically attempt an SSL/TLS connection with your server, and will establish it if your server supports it. So, disabling SSL/TLS in your email software does not prevent SSL/TLS connections when using the PGP email proxy.
PGP Desktop 10.x, Windows XP, Windows Vista, and Windows 7