[Air-l] Legal opinions, please

[Steve Jones]

A colleague at my university posted the message below recently, to 
which there have been no replies on our local list, so I'm hoping 
that there might be some on air-l who can shed light on his inquiry.

Thanks,
Sj

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More frequently, email messages have had an attachment at bottom that
advises the user to "burn this message if it is not for you" or something
like that. Some even threaten legal action if you read the message and it
wasnt intended for you. (huh? I really saw one that had that phrase!) Here is
a milder version, taken from a recent academy posting:

"NOTICE: This email message or attached file(s) may contain information that
may be privileged, confidential, exempt from disclosure and protected by
law.  It is intended for use only by the person to whom it is addressed.  If
you have received this message in error, please do not forward or use this
information in any way, and contact the sender immediately.  Because e-mail
can be altered electronically, the integrity of this communication cannot be
guaranteed."

I have been wondering about the actual legal basis for these messages. After
all, the sender types in the address, the email is sent, and then it appears
in the receivers email account. It would seem the sender has then
relinquished control over content. In fact, copying the text above into this
message seems to be a violation of the NOTICE.

Does anyone know the actual law here, or why these attachments are appearing
more frequently now?