Today I learned that during World War II, the American government committed German mail fraud.
Part of Operation Cornflakes, as it was called, air-dropped bags of correctly-addressed propaganda mail that the US Office of Strategic Services had created into areas where German trains with mail cars had been bombed. The idea was that the Germans would collect all the mail bags that had been thrown from the train and put them back into the mail system. They forged the German stamps at the time, and included a Cinderella stamp inside for the receiver that had Hitler's head drawn as a skull, with a slight rhyming alteration to the words: "German Empire" was turned into "Destroyed Empire."
It totally worked; 3800 of these propaganda mailings were air-dropped and picked up by the Germans in January of 1945, and subsequently delivered to their intended recipients.
Wikipedia doesn't say if it happened more than the one occasion, but I can't imagine the OSS went through all the effort of forging German postage, making their own Cinderellas, acquiring accurate German addresses, typing or hand-addressing all those addresses, and stuffing the envelopes with their propaganda newsletters just to test it out once.
I also found this site, which talks a bit about different propaganda campaigns the Allies had in various European countries. According to their article, the OSS got the addresses from the German public death notices of Nazi soldiers, and sent propaganda to the grieving family members. Harsh, but probably pretty effective. It says they sent hundreds of these by "clandestine means" every two weeks from 1942 on, so that would make it a larger-scale operation than the Wikipedia entry would lead one to believe. Possibly they got the mail into Germany by means other than air-dropping it before 1945.
