Mickey Dunham used to field a lot of homeowner complaints in her years as a community leader in Columbia and later as an ombudsman for the Rouse Co., which developed Howard County's "new town."

But there was one gripe she received constantly from the hundreds of suburbanites who flocked to the planned development. "I got more calls about the mailboxes than anything else," Dunham, 63, recalled recently. "Everybody wanted to know why they couldn't get delivery to their door, why they had to walk half a block or more to pick up their mail."

It was an inauspicious start for the new-fangled mailboxes--tiers of gleaming stainless-steel receptacles in clusters of 12 to 18. Yet, 16 years after the country's first "cluster boxes" were installed in Columbia to mixed reviews, they have caught on across the Washington area and the rest of the nation as well.

"People seem to like them now," Dunham said. "If you lose your dog, you stick a notice on the mailbox. They've become community bulletin boards."

The boxes' biggest booster is the U.S. Postal Service--the federal agency whose refusal to give Columbia door-to-door deliveries first inspired their creation.

"When we started Columbia, we were told the only mail service we could get would be rural free delivery," said Alton J. Scavo, a senior planner with Howard Research and Development Corp. (HRD), the development company started in the 1960s by Columbia founder James W. Rouse.

HRD had to persuade postal officials to accept the concept of cluster boxes, which Scavo said fit in with Rouse's grand design of a Columbia "community." "The benefit to the cluster boxes was that they brought people together," Scavo said.

Because the new mailboxes were experimental, HRD itself had to purchase and install them for all but a handful of Columbia's 18,000 households. But now, because of the cluster boxes' success in Columbia, the Postal Service will provide them to builders who want to install them in new developments.

"Columbia was the first place in this country to try out these collection boxes, and it quickly became apparent--to us, at least--what kind of money they could save," said Frank A. Kreiner, the acting general manager of the Postal Service's route management division. Officials estimate that every 100,000 cluster boxes save $31 million in delivery and collection costs.

Still, the nation's 930,000 cluster boxes, called in postal parlance "neighborhood delivery and collection box units," represent only 1.08 percent of the Postal Service's total urban and rural deliveries, Kreiner said.

"Centralized deliveries, of course, date back many years, but it's only been in the last several years that NDCBUs have grown in popularity," he said.

In addition to Columbia, Washington area communities with cluster boxes include the Fort Lincoln new town development in Northeast, Atlantic Gardens on Fourth Street SE, and the Embassy Park development in Northwest, according to Postal Service spokesman George Conrad. There are about 250 cluster box units in the District.

Northern Virginia, meanwhile, appears to have embraced the concept of centralized deliveries eagerly. Most of the region's nearly 1,500 units have been installed at Vienna's Mayfair at Oakton development and at Vienna Oaks on Chain Bridge Road, Conrad said.

Cluster boxes customarily are installed at a builder's request, leaving residents very little say in their design or placement. (The Postal Service offers a variety of boxes, including some for colonial-style developments, Kreiner said.)

But at the Twinbrook development near Fairfax, residents themselves asked for--and will get--225 Columbia-style mailboxes, according to an officer in the local civic association.

"Cluster boxes are a better alternative for the residents here," said David W. Luengen of the Twinbrook Association. Earlier this year, the association polled residents of the three-year-old development near Braddock and Guinea roads about replacing the old-fashioned, breadbox-style mail tubes with locking cluster boxes.

"There was not one dissenting comment about cluster boxes," said Luengen. "There's no maintenance costs, they're secure--and more weathertight than what we've got now." The association must prepare the installation sites for the new boxes at 12 to 15 points around the neighborhood, however, Luengen added.

The strongest opposition to cluster boxes has come from mail-carrier unions, which complain that the boxes are a threat to their members' jobs and another slap at consumers tired of higher mail prices and service cutbacks.

"Cluster boxes are inconvenient for the elderly and the disabled," said Vincent R. Sombrotto, president of the 250,000-member National Association of Letter Carriers. "Imagine having someone in a wheelchair having to traipse two blocks to get their mail." Most cluster boxes are concentrated in Sun Belt retirement communities.

Sombrotto criticized postal officials for urging the installation of cluster boxes around the country. "The Postal Service is taking away from the individual American consumer, who has no say, in the decision on whether their community is going to get these boxes," he said. "As for the people who ask for them, they've been fooled by the Postal Service."

But top Postal Service officials, facing increases of 2 percent in delivery locations every year, will continue to advocate the use of cluster boxes, they said. "Cluster boxes work," said Kreiner. "They've worked in Columbia and they work from Florida, to North Carolina, to California.

"Door delivery is twice as expensive. Cluster boxes allow us to be more productive."