Recently, I heard chatter about this on a listserve, so I updated my research on this topic and am sharing it here.
One of the biggest flaws of this idea is that the postmark and seal prove something.
- What is to prevent someone from mailing an UNsealed envelope to themselves? It has a postmark. But since it is unsealed, material can be placed in it at any time--2 months later, 2 years later, 10 years later, then sealed.
- Sealed envelopes can be steamed open (and probably opened by many other methods that I don't know), the material replaced with something else, then resealed.
Read what the copyright office itself has to say:
"When is my work protected?
"Your work is under copyright protection the moment it is created and fixed in a tangible form that it is perceptible either directly or with the aid of a machine or device."
The Frequently Asked Questions page is very helpful resource. This page has "Copyright Registration of Books, Manuscripts, and Speeches."
A book recommended by the Author's Guild is The Writer's Legal Guide by Tad Crawford & Kay Murray. It is in its fourth printing.
Here are some articles on this topic:
"Poor Man's Copyright" by Peter Clarke
"Poor Man's Copyright" by ©opyright Authority.com
"How To Copyright a Book" at Go-Publish-Yourself.com begins with this sentence: "Before learning how to copyright a book, you need to learn how not to copyright book."
Want to know more?
Some authors may want to consider an intellectual property rights lawyer. I found some information on copyrights here at intellectual-property.lawyers.com. Here's an interesting post with a Literary Agent Attorney FAQ from Literary-Agents.com.
And here's a column on copyright written by Linda Kattwinkel, who is an intellectual property rights lawyer.
So now you know--poor man's copyright, only a myth.