What does Internet Message Access Protocol 4 (IMAP4) allow a user to do that Post Office Protocol 3 (POP3) does not?

The Internet Message Access Protocol version 4 (IMAP4) allows a user to access and manage their email from multiple devices simultaneously, which is one of its primary advantages over Post Office Protocol 3 (POP3). IMAP4 is designed to keep emails stored on the mail server, allowing them to be viewed and managed from various devices, such as a computer, smartphone, or tablet. Changes made on one device—such as marking an email as read or moving it to a different folder—are synchronized across all devices in real-time.

In contrast, POP3 is more limited in this respect. It typically downloads emails from the server to a single device and then deletes them from the server by default, making it challenging to access the same emails from another device. Therefore, IMAP4's ability to facilitate access to email from multiple devices is the key differentiator that sets it apart from POP3.