Email moves through a chain of protocols, and each one manages a particular task. Among the various retrieval protocols, POP3 is one of the most broadly supported and oldest protocols. It enables an email client to download messages from a mail server and then store them on a local device for reading offline. IMAP has become the default protocol for people who leverage different devices. However, POP3 still caters to backup tools, single-service setups, and legacy systems. In this guide, let us cover the meaning, ports, working process, benefits, demerits, and security facets of the protocol.

What Is POP3?


What is POP3? It stands for Post Office Protocol Version 3 (POP3). It is an Internet standard protocol that email clients utilize to fetch messages from a remote mail server over a TCP/IP connection. Here, the “3” means the third version of the original Post Office Protocol.

  • It operates as a “store-and-forward” service: the server manages the incoming mail until the client downloads it.
  • Messages are often deleted from the server post-download, though numerous clients can be set up to keep a copy of the selected period.
  • It just manages receiving emails. Sending is managed only through SMTP.
  • Most of the email clients support it, including Mozilla Thunderbird, Microsoft Outlook, and Apple Mail.

Read More: The blog explores the difference between POP3 and IMAP. Before proceeding further, it is worthwhile to learn about the fundamentals of what is IMAP.

How POP3 Operates?


The process of retrieval follows the five distinct stages: 

  1. Connect: The email client starts a TCP connection to the email server.
  1. Authenticate: The client can send the username as well as password.
  1. Retrieve: The client sends text-based commands and can download the messages.
  1. Delete or Keep: By default, the server copies can be deleted post-download.
  1. Disconnect: The session is closed, and all new emails exist on the local device.

Technically, a session goes through three main states. The authorization state starts after the server greets the client. Then, the transaction states follow, where responses and commands are exchanged. When the client sends you a quiet command, the session enters the update state, and the server then deletes the downloaded messages before terminating the connection.

Since a POP3 server removes email post-download by default, the messages are associated to the device that fetched them. Users can work around this by setting up the client to leave a copy on the server.

POP3 Ports


The protocol leverages two key ports:

  • Port 110: This is the default port. It has no encryption, so information as well as credentials travel in the form of plain text.
  • Port 995: Called POP3S, it encases the connection in the TLS/SSL encryption.

There are also some servers that provide support to the STLS command, which boosts a simple connection to an encrypted one. Port 995 is the preferred option for any POP3 connection that crosses an unreliable network.

History of POP3


  • 1984: The Internet Engineering Task Force published RFC 918, which was the first version of the Post Office Protocol.
  • 1985: RFC 937 introduced version 2.
  • 1988: RFC 1081 introduced version 3.
  • 1996: After multiple revisions, RFC 1939 established the present specification.

The developers ensured that the design remains simple, and that simplicity explains why POP3 is still widely supported by almost every email client.

What Is the Main Distinction Between POP3 and IMAP?


What Is the Main Distinction Between POP3 and IMAP

What is the difference between POP3 and IMAP? Both receive emails from servers. However, they manage storage distinctly. POP3 downloads emails to the local device and often deletes them from the server, whereas IMAP keeps emails on the server and syncs them across devices.

  • Storage: POP3 pushes email to the local device. IMAP then leaves it on the server.
  • Multi-device Access: POP3 is suitable for one device. IMAP synchronizes read status, folders, and deletions everywhere.
  • Folders: IMAP provides different folders on the server. POP3 does not.
  • Ports: POP3 utilizes 995 and 110. IMAP utilizes 143 and 993.
  • Offline access: Downloaded POP3 mail is totally available offline. IMAP provides offline access mainly to messages that are already cached or viewed.
  • Message loading: IMAP retrieves headers first and downloads the entire content only when the message is opened.
  • Server space: POP3 utilizes minimum server storage. IMAP requires more.

Both protocols only get emails. Sending is managed by SMTP, which often utilizes ports 465, 25, and 587. For an in-depth look at how sending and retrieval fit together, read IMAP and SMTP.

Benefits of POP3


  • You can read the message offline post-download.
  • Attachments open quickly since they are locally stored.
  • Server storage requirements are low, which aids hosting limitations.
  • Limited local storage as per the device’s drive size.
  • The protocol is simple to set up and broadly supported.

Disadvantages of POP3


  • You cannot access mail from other devices by default.
  • There is no synchronization in real-time of deleted, read, or folder states.
  • Exporting a local mailbox to a different computer or another client can be tricky.
  • If a local mail folder gets corrupted, then it can cause the loss of the whole mailbox.
  • Downloaded attachments can make the entire device exposed to malware if your security is weak.

POP3 Security Considerations


POP3 Security Considerations

The protocol was built in an era with less cybersecurity threats. So, it requires a much more detailed configuration:

  • Credential Theft: Logins on port 110 can be captured on the network due to lack of encryption.
  • Local Risk of Malware: Infected attachments directly land on the endpoint.
  • Gaps in Forensics: Deleted copies of server make incident investigation difficult.
  • Compliance conflicts: Automatic deletion can conflict with rules of retention under regulations like GLBA, HIPAA, and GDPR.

Recommended practices:

  • Utilize port 995 with security protocols such as SSL/TLS for each connection.
  • Ensure endpoint security and consistent backups in place.
  • Set up clients to store server copies for a defined period when records are important.
  • Train users to open unverified and unexpected attachments with great caution.

When Should You Use POP3?


The protocol aligns with specific requirements:

  • Email is mostly read from a single computer.
  • Server storage is restricted, or hosting costs must remain low.
  • Field staff or users with unsecure internet require the full archive offline.
  • Automated systems or backup tools need to download mail without affecting server-side states.

For the majority of people who work with tablets, phones, and laptops, IMAP remains a better option.

Conclusion


POP3 is a straightforward and long-standing protocol that downloads the email to a local device for offline use and low server storage. Its key limitations are the lack of multi-device synchronization and its security risks when utilized without encryption. Opting IMAP and POP3 relies on the number of devices a person utilizes, and when local synchronization or control is more important. When POP3 is the best choice, utilizing port 995 and ensuring dependable backups ensures that the setups remain safe.