How to cover this mail slot up so cold air won't come in?

mailbox slot cover   Dan mailbox slot cover

This Taymor mail slot has a sturdy brushed aluminum finish and an interlocking flap and frame Its spring-loaded exterior plate keeps it closed to bl

Mail Slot Catcher for Door Mail Slot, Black Indoor Mail Slot Cover Mail Slot Catcher for Door Mail Slot, Black Indoor Mail Slot Cover

white orchid slot American Key Supply, Inc Mailbox Slot Cover Guard—TEMPLATE The mail slot features an 11-inch wide opening and spring-loaded front plate with an interlocking flap for tight closure It can be easily installed as a