Hi,

Is it OK to vent a dryer vertically into an attic crawl
space

And stopping without going outside??

Nope.

instead of horizontally thru an exterior wall to the
outside?

Go outside! Is the dryer electric, gas? Gas must be vented outside,
there are indoor vent kits for electric dryers but they have a tendacy
to be messy and add moisture where you don't want it

jeff.
Appliance Repair Aid
http://www.applianceaid.com/