The legal standards to prove "conception" of an invention are discussed in Manual of Patent Examining Procedure (MPEP) 2138.04 and Manual of Patent Examining Procedure (MPEP) 715.07. Mailing anything to yourself is not a recognized way to prove "conception."
Save yourself the stamps. Save yourself the envelopes. Save yourself the time.
James Lindon, Ph.D. Patent Attorney
Lindon & Lindon, LLC
Patents, Trademarks, Copyrights, Pharmacy Law, Litigation
[this is not legal advice - provided for discussion only]
Intellectual Property for the Individual and Small Business: Identify, Protect, Enforce, Defend.
"Fools rush in where angels fear to tread."