Mail service, as many have long suspected, can be quite profitable. As a result, public courier services, from the time of those that delivered the Pharaoh's orders in Egypt and Paul's letters in Rome and Corinth, have been matched by private efforts from those who saw quick -- or even slow -- delivery as a good way to make a living.
In fact, one of Benjamin Franklin's acts as colonial deputy postmaster general was to discourage the sticky palms of postriders, who carried in their packets only a few letters on which the postage had been paid, along with a number of others from which only they reaped the profits.
Franklin also instituted the first overnight mail service in this country, between New York and Philadelphia -- a coup for which the United States Postal Service continues to take credit.
But it was this modern need for overnight service that made Fred Smith, founder of Federal Express, a rich man. At Yale University he wrote a paper on what looked to all like a wacky idea - an overnight delivery service using airplanes which funneled all the mail through a sorting center in his hometown, Memphis, Tenn.
The paper received a ''C,'' but the business it outlined, after a shaky start in 1973, pioneered the rapidly growing field of overnight delivery. As a spokesman for Federal put it, ''With the new technology, businesses simply can't afford to wait for more than a day for replacement parts or contracts. We sell time.''
But a spokesman for the Postal Service points out that their express mail, which also promises overnight delivery, started before Mr. Smith's -- and continues to operate at a cheaper cost.
That is because of a constitutional guarantee that grants the Postal Service a monopoly over all first-class mail, except when the mail is especially urgent. For ''urgent,'' read ''expensive'' -- the P.O. spokesman says that Federal's rate of $9.50 for an overnight letter is the minimum that can be charged under the law.
It is certainly not the maximum. A tiny firm in Alexandria, Va. charges $40 for their overnight delivery from Washington, D.C. to Los Angeles, but they promise delivery by 9 a.m. the next day -- three hours before Federal. ''And when you're talking about a million-dollar contract that you may lose by noon,'' says Pat Peck, the firm's owner, ''what's $40?''
Miss Peck got into the mail-sending business by way of the mail-receiving business. About a year ago, she started a lock-box business called the ''Old Town Post Box'' in a city she claims is ''notorious for slow mail delivery.'' For $10 to $25 a month, she promises to get the mail from the city's post office and have it sorted and ready for pickup by her customers four times a day, starting at 9 a.m.
''I deal with a lot of associations, which receive checks in the mail,'' she explains. ''Well, they were getting their checks after the banks closed, and losing a day's interest. That can mount up fast.''
She, like other private mailbox businesses springing up around the country, also caters to ''people working in their homes who want a business address, or people who really want their privacy, or people who take an ad out in the paper and just want an address for a month.''
Firms like ''Fox Plaza Executive Suite'' in San Francisco and ''The Mail's Inn'' in Minneapolis cater to this need for tony addresses and quick service. But Miss Peck says the chatty atmosphere of her office leads to another service - that of business matchmaker.
''I found out that one of my customers is a printer, and another one needed some printing done, so I arranged for them to meet. Some of my customers also are receiving letters from those date-matching services, but I'm not going to introduce them; it's too personal.''
Still, the personal angle may play a part in some of these businesses. One of the five mail-receiving firms listed in the Phoenix phone book, for instance, is ''Belle's Old Time Matchmaking,'' a service that surely does more than provide mailboxes.
Most, however, are like the ''Post Rent-a-Box'' in San Francisco -- lock boxes for those who can't get one of the scarce boxes at their post office. The Postal Service, in fact, has written a pamphlet on how to start a lock-box business for anyone interested in filling this gap, as they look for ways to increase their own supply of the sought-after commodities.
They also appear to welcome private efforts in the delivery end (''as long as they're legal,'' the spokesman cautions). For despite the increased use of alternative postal firms, the volume of US mail -- which last year stood at 110 billion pieces -- continues to rise. As alternative supplier Pat Peck puts it, ''It's still the cheapest form of communication.''