POP3 IMAP and SMTP fro MAIL services


 Post Office Protocol (POP) and the Internet Message Access Protocol (IMAP) are specifically designed for use by individual users retrieving messages and managing mail boxes. 


SMTP is a delivery protocol only. In normal use, mail is "pushed" to a destination mail server


POP3

Post Office Protocol 3     ( download emails )

https://en.wikipedia.org/wiki/Post_Office_Protocol


POP works by contacting your email service and downloading all of your new messages from it

IMAP

Internet Message Access Protocol    ( read emails )

https://en.wikipedia.org/wiki/Internet_Message_Access_Protocol


you aren't actually downloading or storing it on your computer; instead, you're reading it from the email service.

IMAP only downloads a message when you click on it, and attachments aren't automatically downloaded. This way you're able to check your messages a lot more quickly than POP.

Client Commands


Server Response

SMTP

Simple Mail Transfer Protocol

https://en.wikipedia.org/wiki/Simple_Mail_Transfer_Protocol


SMTP is a delivery protocol only. In normal use, mail is "pushed" to a destination mail server