Email Post Office Protocol (POP3) Key Terms

Understanding the terms you need to navigate POP3
By Lesley Graybeal POP3 is the current, standard protocol for retrieving email messages for many email client software programs. Along with IMAP, POP3 is a protocol that communicates with the mail server to download and store email messages, which are then sent to the mail server using another protocol, SMTP. While POP3 is a simple protocol and easy for users to configure, there are some key terms that will help you in setting up and maintaining an email program on your computer.
 

POP3

POP3, or sometimes just POP, stands for Post Office Protocol. The number 3 refers to the third version of the protocol, which has been updated several times since the 1980s. When configuring an email client, you will need to investigate your email server's settings to find whether it is a POP3 or IMAP server and enter the address given into the correct field in your client's settings.
Try: Get a more detailed explanation of POP3 from TechTerms.com or a good background history from The TCP/IP Guide. 

Internet Message Access Protocol, or IMAP

Internet Message Access Protocol, or IMAP, is the alternative to POP3. The main difference between POP3 and IMAP protocol is that while POP3 downloads messages to your computer, IMAP allows you to read messages on your mail client without downloading the message from the server. With IMAP, the message remains in your inbox on the server so that you can read the same messages on any computer.
Try: Learn more about the differences that distinguish IMAP from POP3 with the comparison offered by The Rockefeller University.

User Agent, or UA

User Agent, or UA, is broadly used to refer to the identity of your specific computer as it can be expressed in text to other computers and web servers over the Internet. Your UA also may be synonymous with your email client in the context of POP3 configuration with a mail server, since the way your computer communicates with the server is through the mail client.
Try: Learn more about UA and how it is used on the Internet at What's My User Agent?

Header

The header is a short piece of text at the beginning of an email message, often invisible to the user, that communicates between the mail client and the server when POP3 and SMTP are being used. The header time stamps and identifies the email and also allows mail clients to sort email into proper mailboxes.
Try: PC Magazine provides a definition of an email heading and information about how headers are used by mail clients and SMTP servers.

Node

Node refers to a unit of information contained in an email and sent through POP3 or other protocols. Within the context of POP3, a node is usually understood to be a symbol that stands for a larger body of text or data. Node can also mean a specific point in a network, like a computer, server or peripheral, so that both your computer and the email server might also be considered nodes in a larger sense.
Try: W3C and Bradley University both provide definitions for node within a larger glossary of network-related terms.

Authenticated POP, or APOP

Authenticated POP, or APOP, is an extension of the standard POP3 protocol that is typically used by mail clients and servers. By using APOP, your username and password are encrypted by the protocol and decrypted by the server, allowing your actual password to remain protected.
Try: Read more about APOP from Mails Broadcast and Gordano.