Nonononono ... the whole thing with mailing yourself a copy of your work
is basically to get the post office to put a time/date stamp on it,
proving an original creation date. Sort of like getting it notarized.

Under current US copyright laws, any original text you compose is
automatically under your copyright. You just need to make sure your
authorship is identified. What we're dealing with here is people
*asserting* that right, and giving notice that all usage rights are
*withheld*.  Even when you sell a novel, you are only selling *certain
rights of usage* depending on your exact deal.

People who are putting the standard disclaimers up the question
originally asked are merely acknowledging that they're violating others'
rights but not in an intentionally malicious way. People who are putting
somewhat more complex statements up are usually asking for their story
not to be reproduced, archived, or further derived from without their
express consent.

Nightman