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?

Did they claim to be delivering them?

Yes! Excellent!

A security guard watches the comings and goings of the workers at the factory. He sees Sid Shifty coming out on more than one occasion with a wheelbarrow piled high with old newspapers and other rubbish. Nobody else bats an eyelid, but the security guard just has an odd feeling about it all. He searches the wheelbarrow but finds nothing. What is Sid Shifty up to?

Not sure what is going on yet but Sid Shifty sounds like a suspects name.

[JimCarrey]Reeeaalllly[/JimCarrey]

Is Sid Shifty working with the security guard trying to find something on one of the factory workers?

No he's not

Is Sid stealing the wheelbarrow?

He sure is! Lots of them!

A groaner:

At 1300 hours, a man boarded the #13 bus. Unfortunately, every seat on the bus was taken and there was standing room only. This particular bus company had a rule stating that there may only be twelve standing passengers at one time. Our hero happened to be passenger #13. The ticket dispenser noticed this breach, approached our man and requested that he exit the bus. Not wanting to wait an hour for the next bus, our man refused. The bus conductor got angry and pushed the 13th passenger from the bus. Our man found himself on the street with an 18 wheeler bearing down on him.....

After a short trial the official was found guilty of murder and sentenced to death. On the night of the execution, our villain was strapped into the electric chair. After prayer and suitable preamble, the switch was flipped. Nothing happened. The chair was reset, ceremonies reread, and the switch was flipped. Nothing. Nada. No sparks.

The chair was carefully inspected. Nothing appeared to be wrong with the chair. On hearing about this saga, the judge decided that if the chair failed a third time, that was evidence enough for him of Divine Intervention and the prisoner would have his sentence commuted. After a few days, the prisoner was once more strapped to the chair. The customary rigmarole was carried out......the switch was flipped.....and the condemned man escaped with his life.

Why did the electric chair not electrocute our villain?