post office vs snail mail

post office

noun
  • A place (building, office, shop, or counter) concerned with the business of delivering letters, post or mail and selling stamps, etc. 

  • A party game involving the exchange of kisses. 

  • An organisation that delivers letters. 

snail mail

noun
  • Mail sent physically in the post, especially as compared to email. 

How often have the words post office and snail mail occurred in a corpus of books? (source: Google Ngram Viewer )