I\'m developing an ASP.NET MVC application in which I want to encrypt a short string on the server, using C#, and send it to the client-side.
Then on the client-side
In terms of the simplest thing that could possibly work, it seems that you want a simple form of obfuscation, rather than anything really secure.
Rot-13 might be enough, provided that you're dealing with an audience with ASCII email addresses. If you need to support Unicode, then you might need something slightly more sophisticated.