The first of the following Knowledge Base Articles covers troubleshooting email encryption problems with PGP 10.x. The second is regarding PGP 9.x, but does give better information about how to disable SSL in Outlook.
http://www.symantec.com/docs/TECH149647
http://www.symantec.com/docs/TECH148871
As indicated, SSL must be disabled in Outlook so that PGP can act on outgoing and incoming email. However, PGP will take care of the SSL encryption when it connects to your servers, so there is no security risk of doing this. If Outlook was doing the SSL encryption, PGP would not be able to process your email for encryption and decryption because the email would always be SSL encrypted when it receives the email.