POP3 (Post Office Protocol version 3) is a protocol used for retrieving email messages from a mail server. The process of retrieving an email using POP3 can be explained in the following steps:
1. Connection: A connection is established between the email client and the mail server using the POP3 protocol on port number 110.
1. Authentication: The email client sends the username and password of the email account to the mail server for authentication.
1. Inbox Retrieval: The mail server sends a list of all the emails present in the inbox of the email account.
1. Selecting Messages: Based on the user’s command, the email client selects the email message it wants to retrieve from the mail server.
1. Downloading: The selected email message is downloaded from the mail server and saved in the email client’s designated storage space or mailbox.
1. Deletion: Depending on the email client’s settings, the message may be marked as read, left on the server or deleted.
1. Closing Connection: Once the email client has retrieved all of the messages it requires, a POP3 command is sent to indicate the closure of the connection to the mail server.
Overall, the POP3 protocol is a simple, one-way communication between the email client and the mail server, where email clients are only able to retrieve email from the mail server but cannot send any messages on the server.
