why have email confidentiality notices?

Lots of corporations automatically append something like the following to emails sent outside their own servers:

CONFIDENTIALITY NOTICE: This email communication is intended only for the personal and confidential use of the recipient(s) designated above and may contain information which is subject to Federal and/or State privacy laws. In the event that you are not the intended recipient or the agent of the intended recipient, you are hereby notified that any review, disclosure, or use of the information contained herein is strictly prohibited. Do not copy or use the information contained within this communication, or allow it to be read, copied or utilized in any manner by any other person(s). If you have received this communication in error, please notify the sender immediately, either by response e-mail or by phone, and permanently delete the original e-mail, any attachment(s), and copies.

I’ve never understood this – if you were NOT the intended recipient, why would you keep the message, and not just think it was spam? Or, if you’re feeling charitable, why would you not reply to the sender and tell them they have the wrong person?

I think message like this are added by administrators who don’t grok how email works – it’s an electronic postcard: there is no special security, so if you misaddress it, then who ever gets it, gets it.

Email stops, and potentially is collected, at some many different places along its delivery path that such a “disclaimer” is completely pointless.