You mean mail the card by itself rather than inside an envelope? I suppose, but current USPS rules state that cards have to be a minimum of 3.5" tall, and these older ones are only 3.25" tall, thus they'd be rejected as unmailable or potentially subject to a surcharge. In any case, the card only bears 2¢ postage, and as such would have to have at least 33¢ in additional postage added (for which there may not be sufficient room on a card of this size...).