IMAP4 vs POP3: Key Differences Explained

As we know, SMTP is used to deliver mail to a user’s mailbox. Users then need to access these mailboxes to read their email. This access is accomplished using POP and IMAP protocols.

Let’s explore the differences between IMAP version 4 and POP version 3.

POP3 - Post Office Protocol version 3

POP3 (Post Office Protocol version 3) serves as a message retrieval protocol for accessing internet-based email accounts. It’s defined in RFC 1939.

The process works like this:

1. The client initiates a TCP connection to the POP3 server on port 110.
2. Once the connection is established, the client sends its username and password to the server.
3. Upon successful validation, the user gains access to their mailbox.

The POP3 client sends 4-character commands to the server. The server then responds with a limited set of alphabetic responses. These commands and responses happen behind the scenes, remaining invisible to the email user.

With POP3, users can:

• Delete emails
• Download emails
• List emails

However, POP3 has limitations. Users cannot directly alter or change the content of emails on the server. To make modifications, the user needs to download the email content to their local client machine, make the changes there, and then re-upload (if needed, though POP3 generally doesn’t support uploading changes back). This process introduces delays and increases network traffic due to the content downloading requirement.

IMAP4 - Internet Message Access Protocol version 4

IMAP4 stands for Internet Message Access Protocol version 4.

IMAP addresses the limitations of POP3 by enabling various functions, such as moving, deleting, and viewing messages, without requiring the email content to be copied to the local machine.

The key difference: POP3 downloads the content and then allows operations on the content locally on the client machine. In contrast, IMAP4 allows operations on the content directly on the server without the need for downloading it to the local machine.