Answer:
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.
Sitting down you have it, Standing up you don't.
What never asks questions but receives a lot of answers?
If you can get this professional's attention you can get where you need to go for a price.
Mouth up it gets filled, mouth down it gets empty.
What do you purposefully put lots of in and on your body, but run away from when you encounter it outside?