...This enables your app to not only respond to new emails but also allows it to read and parse existing mails and much more. PHP-IMAP is a wrapper for common IMAP communication without the need to have the "native" php-imap module installed/enabled. The IMAP protocol is completely integrated and therefore supports all IMAP commands including the IDLE operation and the "new" oAuth authentication process. You can enable the php-imap module in order to handle edge cases, and improve message decoding quality, and is required if you want to use legacy protocols such as pop3.