Post Office Protocol (POP) has two main modes of operation: POP3 (Post Office Protocol version 3) and POP2 (Post Office Protocol version 2). POP2 was the earlier version of the protocol and is less commonly used today. It retrieves emails from a server to a client device, deleting them from the server once downloaded. POP3, on the other hand, is more widely adopted and allows users to download emails to their devices while optionally leaving copies on the server. POP3 operates in two modes: delete mode, where emails are removed from the server after download, and keep mode, where copies can be retained on the server.
Various types of mail protocols exist to facilitate email communication and management. Besides POP3 and IMAP (Internet Message Access Protocol), other notable mail protocols include SMTP (Simple Mail Transfer Protocol), which handles outgoing email transmission between servers, and Exchange ActiveSync (EAS), which synchronizes email, contacts, calendars, and tasks between servers and mobile devices. These protocols each serve different functions in the email ecosystem, ensuring efficient communication and management of email services.
POP3 (Post Office Protocol Version 3) is primarily used for retrieving email messages from a mail server to a client device. It allows users to download emails to their local devices, typically using email clients such as Microsoft Outlook or Mozilla Thunderbird. POP3 operates on port 110 by default, or port 995 for POP3S (POP3 over SSL/TLS), providing a simple method for accessing emails while managing storage space on the server by removing messages once downloaded.
The terms “POP” and “POP3 protocol” are often used interchangeably, but they refer to the same protocol—Post Office Protocol version 3. The key difference lies in the context and specificity: “POP” can refer broadly to the family of Post Office Protocol versions (including POP2 and POP3), while “POP3 protocol” specifically denotes the third and most commonly used version of the protocol. POP3 introduced improvements over its predecessor, including support for more efficient message retrieval and management options like message retention on the server.