Do they mean anything?

Are they legally binding?

Here's a garden variety example of one...

"DISCLAIMER: This e-mail and any file(s) transmitted with it, is intended
for the exclusive use by the person(s) mentioned above as recipient(s).
This e-mail may contain confidential information and/or information
protected by intellectual property rights or other rights. If you are not
the intended recipient of this e-mail, you are hereby notified that any
dissemination, distribution, copying, or action taken in relation to the
contents of and attachments to this e-mail is strictly prohibited and may
be unlawful. If you have received this e-mail in error, please notify the
sender and delete the original and any copies of this e-mail and any
printouts immediately from your system and destroy all copies of it."