I sometimes receive an email with an elaborate bunch of legalese appended, telling me that if I'm not the intended recipient then I have no right to retain a copy of it. That someone could think any reasonable human would take such a claim seriously has always boggled my mind!
Some such disclaimers state that even an intended recipient is prohibited from copying the email. If you were to take that seriously, it would prevent you from printing the email, from making a backup copy of your emails...
I've just discovered another fellow's tongue-in-cheek rant on the subject, and no longer feel any need to write my own. I'll simply point you to:
Disclaimers are generally worthless - by Matt Winckler.
(Matt may be misguided on petrol-guzzling SUVs, not to mention Christianity, but at least he's sound on these sorts of disclaimers:-)