Are You Smart Enough To Solve These Riddles?

There is no such thing as a perfect crime.

A wealthy man lives alone in a small cottage. Because he was handicapped he had everything delivered to his cottage. The mailman was delivering a letter on Thursday when he noticed that the front door was ajar. Through the opening, he could see the man’s body lying in a pool of dried blood. On the porch were 2 bottles of milk, Monday’s newspaper, a catalog, flyers, and unopened mail. When Sherlock Holmes got to the cottage he told the police the killer was the mailman.How did he know?