Information Rights Management is a free service from Microsoft which sets specific permissions on your sent emails. If you want that no one should be able to print, copy or forward your sent emails to someone else, then all you need to do is sign up for the Information Rights Management Service. Its very simple, the only requirement is a windows Live ID!
IRM uses a server to authenticate people who create and receive emails with specific permissions. In order to sign up for this service, click the New Email option in the Ribbon and choose Permissions.
Choose whether you wish to sign up for this service or not. Click Next when done, then select whether you have a Windows Live ID or not.
Sign in using your Windows Live ID.
Click I Accept and it will finalize your registration for the Information Rights Management Service.
Now you can easily apply restrictions on your emails, if you wish that no one should be able to forward your sent emails then go to Permissions and check the Do Not Forward option, while creating a new email message.