The first thing that happened was the resume box overflowed.

In the mail room of the Reagan administration transition office, somebody built a stack of pigeonholes to handle the various categories of mail flooding in to the government-in-waiting.

There was a slot for "congrats" and another for "negatives." There was a big box marked "kids" ("Our fourth-grade class is doing a project . . . ."), another for "bills," and even one marked "poems and songs," because people apparently are vying to be the new administration's poet laureate. One of the biggest boxes of all was marked "resumes."

Before the end of the first day, the resume box was so full it spilled over.

A second, much bigger resume slot was set up. It, too, filled quickly to the brim. There were leather-bound resumes, 20-page resumes, printed and perfumed resumes, resumes with original artwork provided by the job-seeker. "I knew there would be resumes," says Ed Stuckey, who works in the transition office's economic affairs "issues cluster." "But this is incredible -- thousands of resumes!"

The 200 or so persons now working at the transition office say they have been deluged as well with notes and calls from people looking for top government jobs. For a while, the transition people considered this a predictable, if tangetial, aspect of their jobs. Now, though, most are fed up.

"You know what kind of people call you at home?" one transition official said the other day. "The jackasses, that's who. I've formally decided that anybody who bugs me at home about a job can go look for work someplace else."

The transition staffers are seeing long-time-no-see friends come out of the woodwork, and some persons on the transition team also are hearing from job-seekers who are passing acquaintances at best. At cocktail parties, people they meet for the first time ask where a resume ought to be sent. A Reagan campaign worker who traveled on the candidates plane this fall reports that one of the flight attendants called to suggest, as she delicately put it, that she "would be interested in entering public service."

The word is out, clearly, that among various other powers available to a newly elected president is the authority to give out hundreds, or even thousands, of top jobs in the federal bureaucracy. They range from Cabinet secretary, a $66,000-a-year policy-making job that is probably not available to the average resume-sender, to all sorts of deputy, assistant and deputy assistant jobs paying $40,000 a year or more. The administration also will name some clerks, chauffeurs and chefs, who will be paid about $20,000 annually.

The official guidebook to such things, a quadrennial government tome formally titled "Policy and Supporting Positions" but more commonly known as "The Plum Book," will be out this week with a list of about 2,700 "Schedule C" [political appointee] slots. But Reagan probably will have 2,000 or 3,000 jobs to fill in addition to these traditional "plums."

Because of the civil service reorganization engineered by President Carter, Reagan will be able to fill about 1,000 "noncareer" jobs in the Senior Executive Service category (salary: $50,112.50 a year) and about twice as many "career" executive jobs.

Some of these jobs will be handed out by the transition office, where Los Angeles executive recruiter E. Pendleton James is in charge of the talenthunt operation. But many will be filled by the people Reagan picks for the top jobs in each agency. And the people who fill most of the top jobs will be chosen by the president-elect and a close circle of old California friends.

But hope springs eternal in the jobseeker's breast. At the transition office (Washington, D.C. 20270), they've added another pigeonhole for the unceasing run of resumes.