Is it possible to soundproof a door with a mail slot?

What is the best way to leave mail for the mail person to pick up if you use a slot in the door for mail to come through? block the box

Typically for Doors & Walls Thicker Than 3 Inches Engineered for maximum insulation performance, our DraftDodger™ Insulated Mail Slots cut drafts, reduce

door mail slot Of equal or greater concern was the possibility the burglars with freakishly small hands could reach through the slot and unlock the front door

door slot lock block at front is for scroll ; holes will aid in carving flutes Top mail from an extruded brass mail slot to a box located in a closet This