Answer:
Sends paper without using the post office.
Tear one off and scratch my head, what once was red is black instead!
Without coolant, you'll have some trouble with this.
What can you hold in your left hand but not in your right hand?
What is in seasons, seconds, centuries, and minutes, but not in decades, years, or days?
What do you purposefully put lots of in and on your body, but run away from when you encounter it outside?