Yes. Even though you will receive an envelope (or printable envelope template) along with your absentee ballot that says "OFFICIAL ABSENTEE BALLOTING MATERIAL - FIRST-CLASS MAIL - No Postage Necessary in the U.S. Mail - DMM 703.8.0," this is not the case for most overseas voters.
In order to have your ballot counted as an overseas voter:
- You must affix correct international postage.
- It must be returned with an overseas postmark.
- It is best to mail it from a post office, in order to verify that you have correct international postage and that it is postmarked to confirm the date it was put into the mail outside of the U.S.
- DO NOT take the ballot to the U.S. and mail it from there, or give it to a friend who is traveling back to the U.S. to put in the U.S. mail. Again, in order to have your overseas ballot counted, it must have an overseas postmark.
- Make sure the election office address on the ballot includes "USA."
Exception: The postage is prepaid ONLY if you are able to get your absentee ballot envelope to a U.S. Military post office (APO/FPO). Otherwise, it is not free to send it by normal international post.