THE FAN MAIL DILEMMA : Very Truly Yours, Jack Tamkin : How would you like to answer 100,000 letters a month?

Jack Tamkin doesn’t mind. It’s his business. Tamkin’s L.A.-based Studio Fan Mail service handles responses for such TV stars as Tim Allen (“Home Improvement”), Dean Cain (“Lois &Clark;”) and David Duchovny (“The X-Files”) and movie names like Jean-Claude Van Damme, Bruce Willis and Robert Downey Jr.

In 30 years in the business, Tamkin has aided many a teen idol--from the “Brady Bunch” kids to Henry Winkler during his ‘70s heyday.

“When they did ‘Happy Days,’ Winkler as the Fonz got 65,000 to 70,000 letters a month--and that lasted two to three years,” says Tamkin, who began in the ‘60s with his Tamkin Color Co. It printed the “autographed” color postcards studios would mass-mail back to fans who wrote to their stars. “I’ve done about 170 TV series. We did ‘Batman’ and ‘The Green Hornet’ and ‘The Beverly Hillbillies’ and ‘Voyage to the Bottom of the Sea.’ ”

After 20th Century Fox asked him to just send out the photos himself after he printed them, Studio Fan Mail was born. Now it is contracted by stars, studios and shows (“Friends,” “X-Files,” “Home Improvement”) to make sure their fans don’t think they’re being ignored.

“We take great pride that everybody that writes in gets a picture,” Tamkin says. “All the letters are read” by his workers after they’re forwarded by the studios, and “everything is handwritten, no computers,” for a personal touch in the addressing.

That doesn’t mean that every letter is personally seen by the star. “It depends on the actor,” Tamkin says. But you never know. “Henry [Winkler] looked at every letter, just about. I used to take them over in big trash cans after we answered them, and he’d sit there and look through them all.”

Tamkin shies away from saying who gets the most letters or how much stars pay him for his service. But he does drop names of celebs he thinks handle it right. Like “Home Improvement” and “Tom and Huck” kid phenom Jonathan Taylor Thomas: “His mother and her sisters answer his mail, but we do all his printing, and I know for a fact he gets a helluva lot of mail.” And Jonathan sees that it gets answered “because he believes fans are one of the reasons he’s here.”

Fans also are one of the reasons that mail isn’t answered by many celebrities: Some fans are truly fanatical. Tamkin printed pictures for Rebecca Schaeffer, the “My Sister Sam” star killed in 1989 by an obsessed admirer.

“That’s why we screen the mail,” Tamkin says. “We don’t want some nut writing. In the last few years, it’s gotten more and more.” His staff keeps track of “repetitive stuff,” and “we alert the authorities and the actor himself.” Tamkin has even studied graphology to analyze handwriting and was certified to testify in court. But it has never come to that.

“Fan mail is just something that comes in,” he says. “A lot of people don’t answer it. Would you?”