POP3
Also known as: Post Office Protocol(POP)
Post Office Protocol (POP) is a standard by which e-mail can be received. POP3 is the latest and most widely used version of this protocol.
E-mail messages are transported over the Internet via SMTP. Once an e-mail message arrives at the mail server of the recipient's e-mail provider, it is stored in an online inbox. Using the Post Office Protocol, messages can be retrieved from this mailbox using an e-mail program.
Most e-mail programs are configured to automatically delete messages from the mail server once the messages have been downloaded from the server.
IMAP is the de facto successor to POP3.
Security
Messages can be downloaded using POP3 only when the correct username and password are provided at the start of the connection. Optionally, connections can be secured with various forms of encryption, such as SSL.
To combat unwanted e-mail, many providers deploy a spam filter. Spam messages are deleted before they are placed in the recipient's mailbox, or suspicious messages are moved to a separate folder within the inbox.
