mailbox vs outbox

mailbox

noun
  • A folder or account for the storage of email; an electronic inbox or mailstore. 

  • A delivery point for mail, a box, compartment or slot for this purpose. 

  • A collection point for mail intended for onward delivery, a secure box or receptacle for this purpose. 

outbox

noun
  • An electronic folder serving the same purpose, for electronic mail. 

  • A box holding papers to be transmitted to others, eg, by mail. 

verb
  • To box better than. 

How often have the words mailbox and outbox occurred in a corpus of books? (source: Google Ngram Viewer )