hsaryan,
in the email blocking is done by a respone rule, it will allow you to block encrypt or allow.
so this way if the message has the sensitive information you can encrypt it...
the newest version of symantec encryption is rebuilt to integrate very closely with gateway email encryption, some of my clients are not renewing their iron ports and are adding message gateway and tie it all together. Under this new setup DLP is actually doing the encryption so you do not have to log into encryption server to confirm it was encrypted DLP tells you it was.
http://www.symantec.com/products-solutions/families/?fid=encryption
http://www.symantec.com/messaging-gateway
hope these links help and explain what is new...