Learn about the IMAP protocol

Internet Messaging Access Protocol (IMAP) is an Internet standard that describes a protocol for retrieving mail from email servers. When using IMAP, you can sync applications on multiple computers to access the same email account, to display the same status and message.

IMAP helps sync emails

Typically, email is stored and organized in folders on the email server. The email client on the computer and mobile device copies the structure, and then synchronizes the actions (such as deleting or moving mail) with the server. With IMAP, you can seamlessly move mail between folders and keep the account view, whether you're accessing the account directly or via the client.

IMAP is a recent and more advanced standard for storing and retrieving mail compared to Post Office Protocol (POP). Readers can refer to the article: Differentiate POP and IMAP for more details.

Disadvantages of IMAP

The advanced features of IMAP make it more complicated. For example, after you send mail via SMTP, it must be sent back via IMAP to save in the Sent folder of the IMAP account.

IMAP is difficult to implement, and IMAP email clients and servers may differ in standard interpretation. Developers may find it difficult to deploy a part and their own extensions, as well as encounter bugs. Users may find the email function to be slow and sometimes unreliable.

IMAP extension

The basic IMAP standard allows for the expansion of individual protocols and commands in it. Many IMAP extensions have been identified or implemented. Some of the most popular utilities are listed below.

1. IDLE activates real-time notifications for received emails.
2. SORT organizes messages at the server so that the email program can fetch certain emails without downloading them all.
3. THREAD allows email clients to retrieve related messages without downloading all mail in one folder.
4. CHILDREN implements a directory hierarchy.
5. AccessControlList (ACL) assigns permissions to each user in each IMAP folder.

A complete list of IMAP extensions can be found in the Internet Message Access Protocol (IMAP) Capabilities Registry. In addition, Gmail also includes a few extensions specific to IMAP.