Isolation
The concept of isolation is not new, however, it has not been available to Microsoft Dynamics CRM until now.
This new version adds the concept of isolation called the sandbox. Plug-ins can now be registered in normal mode, which means without having any kind of isolation. In other words, this mode will allow full trust on the code execution and full access to the server resources as the previous version of CRM 4.0 used to allow. If the plug-in is registered in the sandbox isolation mode, then it will run in partial trust and it won’t be allowed to access to some resources on the server, such as files, registry, database, and so on. The level of isolation, however, allows the access to HTTP and HTTPS web resources for external web services ...