IMAP stands for Internet Messaging Access Protocol and describes a protocol for retrieving messages from an email server. Using IMAP, you can synchronize applications across multiple computers to show the same state and messages.
- IMAP Helps Synchronize Email Messages
- IMAP and Other Email Protocols
- Cons of IMAP
- IMAP Extensions
IMAP Helps Synchronize Email Messages
Email messages are usually stored in folders on an email server. Computer and mobile email clients mirror the server’s structure and synchronize actions (like deleting or moving messages). With IMAP, you can move messages between folders seamlessly and see your account in the same way whether you access it online or via a client.
IMAP and Other Email Protocols
IMAP is a more recent and advanced mail storage and retrieval standard than POP (POP). With POP, messages can only be stored and managed locally. So POP is easier to set up and maintain than IMAP.
But POP has fewer features. No other program can download emails, but an email program can keep a copy on the server for later download. POP allows your client to track which messages have already been downloaded, but this process can fail, resulting in duplicate downloads. With POP, you also can’t use the same email account on multiple devices and have actions synchronized.
Sending emails is not part of the IMAP standard. To send emails, your client must support Simple Mail Transfer Protocol (SMTP).
Cons of IMAP
IMAP’s advanced features complicate it. Messages sent via SMTP must be sent via IMAP to get into the Sent folder of the IMAP account.
IMAP is difficult to implement, and clients and servers may interpret the standard differently. Email functionality can be slow and unreliable for users due to partial implementations, private extensions, bugs, and errors.
The basic IMAP standard allows for protocol and command extensions. Many IMAP extensions exist. Here are a few of the most popular.
- IDLE allows for real-time email notifications.
- SORT sorts messages on the server so email programs don’t have to download them all.
Email clients can retrieve THREAD messages without downloading the entire folder.
- CHILDREN uses a folder hierarchy.
- Each IMAP folder’s Access Control List (ACL) specifies user rights.
The Internet Message Access Protocol (IMAP) Capabilities Registry has a full list of IMAP extensions. Gmail also has a few IMAP extensions.