When it was first suggested that holiday cards be sent to the 50 Americans being held hostage in Tehran, negative voices were heard.

"It might be better to send protest letters to the Iranian Embassy in Washington," it was argued. "We know that letters addressed to Washington will be delivered. We don't know what the Iranians will do with letters we send to Tehran."

However, the idea of sending cards to the hostages was irresistible. Uncounted thousands of cards were sent, perhaps millions. Many carried news updates designed to make life seem less bleak to the hostages.

District Liners who sent cards enclosed messages that said things like, "We haven't forgotten you. President Carter is doing everything he can to free you. He has boycotted Iranian oil, and we have stopped shipping Iran things it needs. We are prodding the United Nations into taking action. Scores of nations tell us they will support us. Keep your spirits up."

As the days wore on, we published pictures of sacks of mail being delivered at the Iranian Embassy on Massachusetts Avenue. Then there were similar pictures that were identified as showing "sacks of mail for the hostages being delivered at our embassy in Tehran." I knew we could believe the pictures taken in Washington. I had my doubts about the pictures sent from Tehran.

My doubts were reinforced when The Washington Post received a letter from one of the hostages, Robert C. Ode. He wrote: "Since our captors do not permit us to receive news of any kind, either by radio, TV, newspapers or recent magazines, we have no idea what is being done by the president, the secretary of state, by members of the Congress or any other official of the U.S. government to protect our basic human rights . . . I believe mail is being withheld from us and we have had no visits from representatives of the U.S. government . . . We receive absolutely no news and are not even permitted to converse with our fellow U.S. citizen hostages in the same room."

That letter was dated the day after Christmas, the day after all those holiday cards were supposedly delivered. We are therefore left with this question: If the hostages had not received the tens of thousands of holiday cards that included news of our efforts to free them, to whom were those cards delivered -- the Tehran city dump? POSTSCRIPT

Mrs. Charles W. Harter of Alexandria writes: "We have been disappointed not to see anything in your column about the display of yellow ribbons for the hostages.

"The trees around the State Department all have yellow ribbons tied to them. Blackie's House of Beef has them not only at the entrance but on all the posts around the construction area. Conn & R has them on lampposts, and the Giant where I shop in Bradlee Shopping Center on King Street in Alexandria has them at each checkout and on all the posts outside.

"Many private homes also are putting out yellow ribbons.

"Some radio stations are playing the song, 'Tie a Yellow Ribbon.'

"I think this is a 'people' thing instead of sponsored, but how about helping us out in your column?"

You bet. The ribbons will have no impact on the Iranians, but they will be constant reminders to us each time we see one.

In an era in which it is easy for people to become preoccupied with their own personal problems, those ribbons will give us a mental poke in the ribs every time we see them.

They'll be a reminder that an injustice remains unremedied. They will help us to like Tam O'Shanter's wife, "gathering her (our) brows like gathering storm, nursing her (our) wrath to keep it warm."

Incidentally, you might be interested in a discussion I had a few nights ago with Martin Weil, one of my colleagues on the late, late shift. "The one thing that baffles me about the Ode letter," I said, "is that the students let it get through. They censor everything -- in and out. Why were they stupid enough to let a letter go through that tells the truth?"

"People make mistakes," Martin said with a shrug. "Even students. Then again, perhaps it wasn't a mistake at all. Maybe it was done deliberately."

"Why?" I asked.

"They think that Carter and Vance are stubborn fanatics but that most Americans are not," he said. "They think our people would like to trade the shah for the hostages. Maybe they figured it would help them make the trade if they let some letters get through showing what a hard time the hostages are having. They want us to pressure our 'false leaders' to make the trade."

Students, you get an F as in failure. And if your embassy in Washington was worth a damn, it would tell you how badly you have misjudged the American people.