I have a few questions....
1. What is the standard postcard size???
2. Does it have to be rectangular or does the post office allow odd-shaped postcards? (hearts, stars, circles etc?)
3. Does the post office allow for them to be 3 dimensional???
i just did some research at the USPS website and this is what i found:
You may think that your mailpiece is a "card," because it is a single sheet of paper. But to qualify for mailing at First-Class Mail card rates, a card must be:
* At least 3-½ inches high x 5 inches long x .007 inch thick (they later said this is as thick as a index card)
* No more than 4-Ό inches high x 6 inches long x .016 inches thick
If your mailpiece does not meet the dimensions above, then the Postal Service considers it a letter (and charges letter rate postage). With Standard Mail, there is a little more flexibility -- there is no separate (lower) postage rate for cards, so you don't have to worry about your postcard being too big -- because you're paying letter rates anyway. But make sure that your card is no larger than 6-1/8" x 11-1/2" x 1/4" thick. Larger than any of those dimensions and you'll have to pay flat (nonletter) postage rates.
Some mailers want to attach stickers, magnets, or other items to their cards. However, an attachment may disqualify a card for mailing at the First-Class card rateor even make it nonmailable. The rules about attachments to cards are restrictive, so check with your local mailpiece design analyst (MDA) or business mail entry staff, who can tell you if your mailpiece design will be mailable.
you can read more for yourself here:http://www.usps.com/businessmail101/mailcharacteristics/cards.htm