Back to Glossary
Email Protocols

POP3(Post Office Protocol version 3)

An older email protocol that downloads messages from a server to your local device.

Definition

POP3 (Post Office Protocol version 3) is an email retrieval protocol that downloads messages from a mail server to your local device. Once downloaded, emails are typically deleted from the server (though this can be configured). Unlike IMAP, POP3 does not sync across devices, so emails are only available on the device that downloaded them. POP3 was designed in the era when people used a single computer and internet connections were slow and expensive.

Why It Matters

POP3 is becoming less common but is still used in some legacy systems. Understanding it helps when troubleshooting customer email issues or migrating from older email systems. Some users prefer POP3 for privacy since emails are stored locally rather than on a server. If a customer says they cannot find your email, knowing whether they use POP3 helps diagnose if it was downloaded to a different device.

How It Works

POP3 connects to a mail server, authenticates, downloads all new messages, and optionally deletes them from the server. It is a simple, one-way protocol without the synchronization features of IMAP. Each email check creates a new connection. The protocol uses commands like USER (username), PASS (password), LIST (show messages), RETR (download), and DELE (delete).

Example

A small business owner has used the same desktop computer for 10 years with POP3 configured. Every time they check email, Outlook downloads new messages and deletes them from the server.

When they try to check email on their new phone, they see no messages - all the emails exist only on their desktop computer.

This is why POP3 can be problematic in today's multi-device world. To keep messages on both devices, they would need to switch to IMAP.

Best Practices

  • 1Consider migrating to IMAP for better multi-device support
  • 2If using POP3, configure it to leave copies on the server as backup
  • 3Use secure POP3 (port 995) with TLS encryption
  • 4Set up regular local backups of downloaded emails
  • 5Document which device has the POP3 email archive for your organization

Frequently Asked Questions

POP3 is less common today but still used for specific use cases like archiving emails locally, privacy-focused setups, or legacy system compatibility. Most users prefer IMAP for its synchronization benefits.

Technically yes, but it is not recommended. Since POP3 downloads and can delete emails from the server, only one device would have each email. IMAP is better for multiple devices.

First, export your locally stored POP3 emails to a backup file. Then configure your email client with IMAP settings. Finally, import your old emails to the IMAP server so they are available across all devices.