The history of POP3 (Post Office Protocol version 3) traces back to the early days of email protocols. Here’s a summary of its development:

1. POP1 and POP2: In the 1980s, email systems relied on protocols like POP1 and POP2 for retrieving email messages from a mail server. These early versions of POP were relatively simple and lacked some of the features later introduced in POP3.
2. Introduction of POP3: POP3 was defined in RFC 1081 in 1988 as an improvement over its predecessors. It aimed to provide a more efficient and reliable method for email retrieval from a mail server.
3. Key features of POP3: POP3 introduced several features that made it widely adopted for email retrieval. Some of its key features include the ability to download email messages to a local client, delete messages from the server, and manage folders on the server.
4. Operation of POP3: POP3 operates on port 110 by default. The protocol follows a client-server model, where the email client (POP3 client) connects to the mail server (POP3 server) to retrieve messages. The client sends commands to the server to authenticate, list available messages, retrieve specific messages, and manage the mailbox.
5. POP3 and offline access: POP3’s design was particularly suitable for users who needed offline access to their emails. Since POP3 downloads messages to the client device, users could read and manage their emails even when not connected to the internet.
6. Evolution and enhancements: Over time, enhancements were made to the POP3 protocol to address various limitations. Some extensions introduced features like support for encrypted connections (POP3S) and additional commands for managing mailbox status and message status.
7. Competition with IMAP: In the 1990s, another email retrieval protocol called IMAP (Internet Message Access Protocol) emerged. IMAP offered more advanced features, such as the ability to access and manage emails directly on the server, sync email folders across devices, and search capabilities. This led to competition between POP3 and IMAP, with IMAP gaining popularity for users who needed more comprehensive email management.

Despite the competition from IMAP, POP3 continues to be used, especially in scenarios where offline access and simple email retrieval are sufficient. It remains a widely supported email retrieval protocol, and many email clients and servers offer support for POP3 alongside IMAP.