I imagine many of you are thinking, don't be cruel, Pandora - give us a hint!

Holy moley, it's the stamp thing?!! Thanks, "Brewster's Millions"! (Classic Richard Prior movie if anyone hasn't seen it)

Does it have to do with where the stamp was post marked? Like was it an Elvis stamp and he mailed it to a fake address in Memphis, TN?

You're hot, Jimbo! Think about what gets stamped onto a letter about to be sent back.

return to sender - an elvis song

You got it, Redz!

A group of healthy men walked up a mountain one afternoon. One of them died a painful death, the others were fine. The dead climber was a very active sportsman; he had even spent the morning at the beach. If the man who died had climbed the mountain on any other day, he would have lived. What happened?

Is the fact that he was at the beach important?

Very

Does it have anything to do with altitude? Was he scuba diving and then climbing where the air is thin and it messed with his lungs?

nitrogen bubbles from scuba diving perhaps

Yes! You're really good at these, Jimbo and soot. Here's an answer that was posted 20 years ago for this problem and I think it also works:

The man had been a real Julie Andrews fan. When he reached the top of the mountain, he was struck by its similarity to the setting in The Sound of Music.
Unable to contain his delight, he burst into the title song in a believable falsetto. His voice was carried far and wide by the gentle breeze.
By coincidence, a stag was passing through on a new (to him) migratory route. When he heard the singing, he tilted his head to listen.
Upon identifying the song, and thereby the movie, the stag flew into a rage and charged toward the clearing. He HATED that movie. He especially hated the song about the doe (Doe, a deer...) that didn't even MENTION a stag! It's not as if they couldn't have worked one into the movie somehow!
Blinded by his anger, the stag hurled himself upon the hapless mountain climber and stomped and trampled him to death.

Next up:

A gang of criminals was loading a van with television sets that they were stealing from a warehouse when they suddenly heard the siren of an approaching police car. They could not avoid or outpace the police car. The gang did not try to escape, instead they thought laterally. How did they escape?