BIRMINGHAM, Ala. — Hundreds of thousands of holiday cards and letters thanking wounded American troops for their sacrifice and wishing them well never reach their destination. They are returned or thrown away unopened.

Since the Sept. 11 attacks and the anthrax scare, the Pentagon and the Postal Service have refused to deliver mail addressed simply to "Any Wounded Soldier" for fear terrorists or opponents of the war might send toxic substances or demoralizing messages.

Last season, despite the rule, officials say as many as 450,000 pieces of mail not addressed to anyone in particular managed to reach Walter Reed Army Medical Center in Washington. But they were returned or thrown out, because the hospital lacked the manpower to screen all the mail, spokesman Terry Goodman said.

"A lot of this is because of security concerns because it's unsolicited mail that someone is going to have to go through," Goodman said. "Also, being a democratic society, there could be inappropriate mail from someone who, say, doesn't support the war, and then you've got a wounded soldier getting it."