Logic Riddles

Question: what did the postman say to the mailbox?

Question: A town builds a bridge, but this bridge can only hold three people at a time or it will collapse. One night, a baker, a flourist and a butcher go on the bridge, and it collapses. Why did it collapse?

Question: Two men went into a restaurant. They sat at a table and the waiter came by and asked, "What do you want to drink?"

The first man said, "I'll have H₂0."

The second man said, "I'll have H₂0 too."

The second man died.

Why?

Question: A man is doing some work on his home and goes to a hardware store. He goes up to the clerk and tells him what he wants. The clerk tells him that each one is $1. He tells the clerk he would like 5000 and he is charged only $4.

What did he buy?

Question: My first is in yesterday, but not in today; My second is in after, but not in before; My third is in start, and also in stop; My fourth is the 20th letter of the English alphabet; My fifth is in correct but not in wrong; and my sixth is in pretty, but not in cute. My whole is something celebrated by Christians. What is this teaser referring to?