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Post Office Protocol

Post Office Protocol

(also POP, POP3)

Post Office Protocol definition

The Post Office Protocol (POP) is an internet standard protocol used for receiving email from a mail server. It is also commonly known as POP3 (version 3), which is the most widely used version. POP3 is part of the Internet Message Access Protocol (IMAP) family and is specifically designed for downloading emails from a mail server to a local email client (e.g., programs like Outlook or Apple Mail).

See also: client, email attack

How the Post Office Protocol works

  1. You have an email account with a POP email provider.
  2. When someone sends you an email, it’s stored on the provider’s server.
  3. You open your email client (e.g., Outlook).
  4. Outlook connects to the server using POP.
  5. POP downloads the email to your device (e.g., smartphone).
  6. The email is now on your device; you can read and manage it offline.
  7. The email is typically removed from the server, but you can configure settings to keep copies.


  • IMAP (Internet Message Access Protocol) is a protocol that keeps emails on the server and syncs them across devices. It needs an internet connection to access emails and is suitable for users who check email from different devices.
  • POP (Post Office Protocol), on the other hand, is a protocol that downloads emails to your device but doesn’t sync them across devices. It can access emails offline and is better for users who primarily check their email on one device.

Further reading

Ultimate digital security