IMAP (Internet Messages Access Protocol): originally developed in 1986 by Mark Crispin, it’s a client/server protocol.
It is an email protocol that is used to access email messages in a remote web server from a local client, it is an application layer email protocol. Its well-known port address is 143.
The emails messages that are received are kept by the internet server, it can work on a slow connection.
IMAP Protocol is one of the two most used protocols used to retrieve information from the mail server, almost every mail clients and mail server support IMAP and POP3.
IMAP allows you to access, read, organize and sort your email messages without having to download it first. As a result; IMAP is very fast and efficient as whenever you check your mailbox it connects to the server and it’s possible to check your email from different devices without missing a thing.
The easiest way to understand how IMAP works is by thinking of it as an intermediary between your email client and your email server.
Email servers are always used when sending and receiving email messages. With IMAP, though, they remain on the server unless you explicitly delete them from it. When you sign into an email client like Microsoft Outlook, it contacts the email server using IMAP. The headers of all of your email messages are then displayed. If you choose to read a message, it is quickly downloaded so that you can see it – emails are not downloaded unless you need to open them.
There are several advantages to using IMAP:
1. It allows you to access your messages from anywhere via all devices you want.
2. It only downloads message when you click on it.
3. Attachments are not automatically downloaded
4. IMAP can be used offline (like POP)