Answer:
What is so delicate that even mentioning it breaks it?
This is a dead giveaway
What can travel around the world while staying in a corner?
You're currently trying to solve one
Lots of them make up a word, And lots of words are in them. It's easy when you think about it. A while ago we stamped and mailed them.
What do you purposefully put lots of in and on your body, but run away from when you encounter it outside?