Hello,
Please see these two articles that address this issue. Let me know if you still have questions.
Many Unexpected Pop-Ups from Symantec Email Proxy are Displayed
http://www.symantec.com/business/support/index?page=content&id=TECH122425&actp=search&viewlocale=en_US&searchid=1319474424929
Unexpected Pop-Ups from Symantec Email Proxy
http://www.symantec.com/business/support/index?page=content&id=TECH152343&actp=search&viewlocale=en_US&searchid=1319474356083
Moving this thread to the Endpoint Protection forum for greater visibility.
Thomas