What is and how does a POP3 Mailbox work?

Both in private and official as well as in business correspondence, email has now become the preferred means and has replaced the physical letter in its significance. While the communication between individual mail servers is invisible to the user based on the Simple Mail Transport Protocol (SMTP), the retrieval by a client is done either through the Post Office Protocol Version 3 (POP3) or through the Internet Message Access Protocol (IMAP). Both differ significantly in their technical aspects and have their own advantages and disadvantages that a user should consider for optimal mail hosting. With POP3, it is a classic network protocol for the transmission of information, but it is limited in its functionality and does not offer the numerous possibilities of extensions like Microsoft Hosted Exchange.

POP3 is specifically designed for the transmission of emails

The Post Office Protocol dates back to a time before the existence of the current internet and was standardized in its first version in 1984, and later in its current version POP3 in an official paper (Request for Comments, RFC 1081) four years later. It describes the process by which a recipient (client) can retrieve their emails from the mail server to store them locally. It handles this task very well and proceeds as follows:

• POP3 client connects to the mail server and authenticates using a password
• Client retrieves new messages for the email address
• Server sends emails to the client
• After transmission, the server deletes the messages

In its process, POP3 is very efficient and requires only minimal bandwidth. At the same time, it has significant advantages for the provider - usually an Internet Service Provider (ISP) - as it assumes that the messages are stored and composed locally on a single device. However, this also entails some disadvantages for the user, which should be considered when choosing between POP3 and IMAP.

POP3 protocol is designed for local storage of emails

With POP3, a method is used that standardly involves storing and processing messages locally without a permanent connection to the mail server. This means a message is temporarily stored upon arrival at the email address and delivered to the user upon the next access. This principle is similar in some aspects to that of a traditional mailbox and is often compared to one - incoming messages are ready for retrieval in the mailbox, while outgoing ones are composed on a remote computer and sent after completion. While this method offers some advantages, it also presents significant drawbacks for the user in many areas, making its use advisable only under certain conditions.

Limitations in functionality with POP3

By design, POP3 is relatively simple and, on one hand, very efficient, but on the other hand, it is limited in terms of functionality. This simplicity makes both usage and syntax easier, but it restricts flexibility in more complex situations. Essentially, POP3 only allows the following actions and functions:

• User authentication by name and password
• Checking the status of an email address
• Retrieving all messages or a specific email
• Marking incoming mail for deletion after the connection ends
• Logging out from the mail server and executing deletion operations

Overall, POP3 is well-suited for quick, simple, and reliable message management due to its limited command set. However, the lack of options also leads to significant disadvantages for the user if they deviate from the traditional model or wish to manage metadata alongside messages. These tasks, beyond typical mail hosting, often require additional services such as Microsoft Exchange Hosting.

Differences between POP3, IMAP, and Hosted Exchange

The key disadvantages of POP3 initially lie in the lack of synchronisation between different devices. An email that has been retrieved and deleted from the server is only available on the device used - this also applies to a written but not yet sent message. However, a client does not need a permanent connection to the mail server and can work on messages even without a current network connection. In contrast, IMAP uses a completely different concept - it is not a traditional protocol for mail hosting, but a method that integrates a file system developed for emails on a remote server locally on a computer. Microsoft Exchange Hosting also offers additional options such as integrating other products like the calendar or address book and synchronising across multiple devices.

Photo: Image by rawpixel on Pixabay.com