What is the mailing address to heaven?

First, place your letter in an envelope with only the return address. After that, attach your envelope to a recently baptised baby... then kill the baby. All that's left is to wait for a reply. Alternately, depending on the faith you adhere to, a dog can be used in place of a baby... because everybody knows, "all dogs go to heaven".

p.s.

You may want to say a few Hail Mary's while you wait for a response...