USA Taxes - Just a reminder - April 15

For those out of the country however, you can file for an automatic extension of 3 months I believe (double-check, might be 2). So if you owe money, you can put it off a few months longer;)
Is a stamp from Correo Argentino considered to be a proof that you did not miss the deadline?
Tax returns must be mailed by April 14th., my accountant says any mail stamp would do. Make sure the stamp is legible - sometimes they are so smudged that they are impossible to read.

I seem to remember someone saying that they could be delivered at the American Consulate. Anyone knows about that?