3
airmail
black
blank
box
boxes
business
communication
contact
correspondence
countryside
creativity
deed
delivery
email
exterior
grey
grunge
horizontal
label
letter
letter box
letterbox
mail
mailbox
mailing
message
metal
news
nobody
object
old
outgoing
plate
post
postage
postbox
receiving
retro
row
send
sign
slot
symbol
traditional
vintage
yellow