The annoying, yet necessary disclaimer

After having a not so nice experience, I have decided to start using those very annoying disclaimers at the bottom of my email:

"This email and any files transmitted with it are confidential and intended solely for the use of the individual or entity to whom they are addressed. If you have received this email in error please notify the system manager. This message contains confidential information and is intended only for the individual named. If you are not the named addressee you should not disseminate, distribute or copy this e-mail. Please notify the sender immediately by e-mail if you have received this e-mail by mistake and delete this e-mail from your system. If you are not the intended recipient you are notified that disclosing, copying, distributing or taking any action in reliance on the contents of this information is strictly prohibited."

I used to be annoyed whenever I received an email containing one of these. Unfortunately you might have to face a situation in which an email you sent is being distributed without your knowledge or authorization; or reaching places it should not reach at a given moment. For these cases, then, I recommend to add these confidentiality disclaimers to your messages. If not a bullet-proof legal resource (is there any?) at least it can prevent people from circulating your emails without giving it a second thought.