longish
stale
long time no hear
go all around the Wrekin
nixie
French leave
letterless
airletter
nonreturnable
drawn-out
early days
TL;NR
nonreceipt
go jump in the lake
unreceived
unreplying
take a long walk on a short pier
aeon
kindly
eon
yours faithfully
cheers
note
mail-in
unretorted
too long; didn't read
behind time
ship letter
it's about time
lengthly
noncorrespondence
hello there
epistle
back at you
jot
block letter
misaddress
Rome wasn't built in a day
overprotracted
nonresponse
correspond
responselessness
month of Sundays
aerogram
ambulance cover
hello yourself, and see how you like it
nonreply
mora
post
inside address
overlong
aerogramme
pang seh
airmail letter
sorry I'm late
rough sledding
belay my last
air letter
yours truly
lateish
DNA
sesquipedalian
literal
missive
dead letter
bless up
at bay
mismail
tardy
nonreplying
sesquipedalia
complement
unreplied
forever
overlate
underacknowledged
promiselessness
ungained
unadvised
out of pocket
latecoming
overtime
scrawled
brief
miss
pittance
unreached
crank letter
mailing
nonarrival
hold the floor
overread
welcomeless
anciently
until the cows freeze over
misbox
until the cows come home