Californians dreaming of becoming mailbox millionaires by winning some out-of-state lottery have had those dreams dashed by the U.S. Postal Service, which ruled that six states allowing mail-in lottery business are violating a federal law banning use of the mails to further a lottery. The action was especially tough to take for Bob Frank, a Sacramento man who calls himself "Mr. Lottery." This week, Frank--a gaming buff who sports "LOTTERY" plates on his DeLorean automobile--began circulating flyers offering to sell, for $3 each, the addresses of win-by-mail lotteries in New York, Michigan, Maryland, New Hampshire, Massachusetts and Rhode Island. Officials of some states have indicated that they still believe that by-mail lottery play is legal, based on court precedent, and have turned the Postal Service ruling over to their lawyers. Officials of California's long-stalled lottery--scheduled to begin this fall--said that they have no plans to accept by-mail purchases.