Email Protocols: SMTP, POP and IMAP

• SMTP


  Simple Mail Transfer Protocol, an application layer protocol for handling outbound email
• SMTP operation


  1. Client sends email to mail server

  2. Mail server connected to network/internet

  3. Mail server has database linked to DNS to find destination mail server
• POP


  Post Office Protocol, an inbound email protocol that works at the application layer
• IMAP


  Internet Message Access Protocol, an inbound email protocol that works at the application layer
• POP vs IMAP


  POP does not keep server and client in sync, IMAP keeps them synced
• POP


  Deletes emails from server once downloaded by client
• IMAP


  Keeps a copy of emails on server, only deletes when client deletes from their account
• IMAP


  Allows access to emails from multiple accounts, POP only allows access from one account