The next time you reach for a tissue, you could be wiping your nose with one of those Ed McMahon you-may-already-have-won notices.

The Postal Service is launching a drive to help recycle undelivered bulk business mail - read: junk mail - into everything from toilet paper to pizza boxes.Every year, 4.3 billion pieces of junk mail fail to reach the intended recipients because of outdated mailing lists.

"As a result, who gets left holding the bag? The U.S. Postal Service. As far as the Postal Service is concerned, that is a big problem," said Charles Vidich, environmental compliance coordinator for the agency's Northeast region.

Instead of throwing the catalogs and other come-ons in the garbage, as it does now, the Postal Service hopes to collect it at its huge mail-sorting centers around the country and then invite recyclers to take it away for free.

In the Northeast, the program resulted in the recycling of up to 40 percent - 16,000 tons - of undelivered junk mail this year, Vidich said. The region's 3,000 post offices hope to recycle all errant junk mail by 1995.

But call it junk mail at your own risk.

"We don't refer to it as that ever, ever, ever. There's a lot of money in that industry," said Dominic Bratta, manager of maintenance for the Postal Service's main sorting facility in Melville, N.Y. Instead, it's called bulk business mail. Third-class delivery.

The Postal Service is understandably reluctant to demean an industry that paid it $9.2 billion in postage last year - one-fifth of the agency's revenue.

Moreover, its own survey found that most Americans read junk - ahem, third-class - mail and find it useful or interesting.

Besides preserving precious landfill space, the recycling program could save the Postal Service about $2.28 million a year in the Northeast by cutting disposal costs, Vidich said.

The promise of a steady supply of junk mail could win over recyclers who normally are reluctant to accept glossy advertisements, which are harder to recycle than plain office paper or newsprint.