Message encryption

[signaldeveloper at gmail.com]

I am looking for an open source solution to the world of "message encryption" and be cautious- I mean the kind that when someone clicks a button, instead of delivering the recipient an actual email, it sends them a website link to which they have to log into check the email. This is more of a compliance requirement. 

It's too expensive to have a vendor do it so I'm looking to do it internally for a customer. 

Any ideas? I didn't know if Amavis had some type of thing built in. I seen they have some type of DLP. 


- Paul