Have you ever wondered why there are so many different email disclaimers? That fine grey print at the bottom of nearly every incoming email that hits your Inbox. You may already have one set by your IT department/provider.
Here is a great site that has a variety of formats and uses for email disclaimers http://www.emaildisclaimers.com/Sample_disclaimers.htm
Also, this is the one we use at ICTAA which you are free to reuse:
This communication is intended only for use of the addressee and may contain legally privileged and confidential information. If you are not the addressee or intended recipient, you are notified that any dissemination, copying or use of any of the information is unauthorised. The legal privilege and confidentiality attached to this e-mail is not waived, lost or destroyed by reason of a mistaken delivery to you. If you have received this message in error, we would appreciate an immediate notification via e-mail to admin@yourdomainname and ask that the e-mail be permanently deleted from your system.