To = đến
From = từ
However, when "from" and "to" appear on the envelope we translate them a little bit different
From(Ngừoi gửi) (top left)
______________
______________
To(Ngừoi nhận)(bottom right)
_________________________
__________________________
-You dont have to write both of these words on the envelope. Just write name and address of sender and receiver on the right place.
To older person:
Kính thưa ông(grandpapa)/ bà(grandmama)/ ông bà(grandparents)/ Chú(uncle)/ cô(aunt)/ anh(brother)/ chị(sister)... (this way is very formal)
or
Ông(grandpapa)/bà(grandmama)/ông bà(grandparents)/Chú(uncle)/cô(ant)...
thương mến/thân yêu! (This is a very popular way to greet, and it appropriates to any body)
To your friends (about your age):
Name of the receiver thân mến/thuơng mến/thân yêu!
"Sincerely" "Yours Truly" "Love" =
To older person: Thương
To friends: Thân
Note: This advice only appropriates to use in normal letters (like to say how is any thing going stuff)-Sorry I dont know how to translate "thư hỏi thăm"