Networking - POP3

POP3 (Post Office Protocol Version 3)

POP3 stands for Post Office Protocol Version 3. It is a standard email protocol used to receive emails from a mail server to your computer or device. POP3 allows users to download their emails from the server so they can read them even when they are offline.

Simple Explanation:

Think of POP3 like a post office that holds your mail until you come to collect it.
When you open your email app (like Outlook or Thunderbird), it connects to the mail server using POP3, downloads all your emails, and usually deletes them from the server after they are delivered to your device.

This means your emails are stored locally on your computer or phone, not on the server anymore (unless you choose to keep copies there).

How POP3 Works (Step-by-Step):

  1. You open your email application.

  2. The email client connects to your mail server using POP3.

  3. The server authenticates you (checks your username and password).

  4. Emails are downloaded from the server to your device.

  5. Usually, the emails are deleted from the server after downloading (optional setting).

Common POP3 Port Numbers:

  • Port 110 – Default port (not encrypted).

  • Port 995 – For secure encrypted connections (POP3S using SSL/TLS).

Advantages of POP3:

  • You can read emails offline, since they are stored on your device.

  • Saves server space because emails are usually deleted after download.

  • Simple and fast for users who use only one device to check mail.

Disadvantages of POP3:

  • Emails are stored on only one device, so you can’t access them from multiple devices.

  • If your device is lost or damaged, you may lose your emails.

  • Limited synchronization — if you delete or read an email on one device, it won’t update on others.

Example:

If you check your Gmail or Yahoo mail using a desktop email app (like Microsoft Outlook) and choose the POP3 setting, the emails are downloaded to your computer. After that, even if you disconnect from the internet, you can still read them.

In Summary:

  • Full form: Post Office Protocol Version 3

  • Main use: To receive and download emails from a mail server

  • Storage: Saves emails locally on your device

  • Best for: Single-device users who want offline access

 

So, POP3 is like a mailman who brings your letters (emails) from the post office (server) to your home (computer) — and once delivered, they are yours to keep locally.