what is SMTP ?

  • it stands for Simple Mail Transfer Protocol.
  • RFC 2821.
  • It is a TCP/IP protocol that specifies how computers exchange electronic mail. It works with post office protocol (POP).
  • Transfers messages from sender’s mail server to recipient’s mail server.
  • Push protocol, not a pull protocol.
  • SMTP is a Principle Application Layer.
  • Push (from client to server or server to server).
  • Pull (from server to client).
  • Email server port is a 25.
  • SMTP server have database with user’s email address, linked to the to the DNS.
  • To know more about SMTP please check Wikipedia link Click here .

What is POP3 ?

  • it stands for Post Office Protocol third.
  • RFC 1939.
  • POP3 is simple and limited in functionality.
  • Uses TCP port 110.
  • To know more about POP please check Wikipedia link Click here.
smpt & imap or POP3 work

Download and delete mode

  • Retrieves messages on server and store the locally
  • Delete messages on server


  • Difficult to access email from multiple computers – work and home.
  • Some email may have already been downloaded on another computer (work) – download-and-delete.
  • To read email from another computer, must leave on server-download-and-keep
  • Does not provide means for user to create remote folders on mail server

What is IMAP ?

  • it stands for Internet Message Access Protocol.
  • Another mail access protocol is Internet Mail Access Protocol (IMAP).
  • IMAP is similar to POP3.
  • IMAP is more powerful and more complex.
  • RFC 2060.
  • Mail not downloaded, but kept on server.
  • Received email is associated with user’s INBOX.
  • Users can create and manage remote folders.
  • Users can retrieve portions of the email
    • Message header: Subject line and Sender
  • To know more about IMAP please check Wikipedia link Click here

Basic Engineer

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