IMAP is the most popular protocol for communicating with e-mail servers. Gmail and many other e-mail services provides IMAP support.
E-mail clients like Gmail Notifier Pro are using IMAP to connect and communicate with IMAP servers,
for example the Gmail IMAP server. Traditionally, the e-mail client connect to the server, check for new messages and then disconnect.
This operation is performed with an interval of a few minutes, to be able to find any new messages as fast as possible.
IMAP IDLE is an addition to the IMAP protocol, supported by some IMAP servers, including Gmail. When IMAP IDLE is used, the IMAP
client will make a connection to the IMAP server, and keep the connection open. The IMAP server will then be able to notify the IMAP
client immediately when a new message arrives. The main benefits are faster notifications of new messages and fewer number of connect
and disconnect operations.
Gmail Notifier Pro support IMAP IDLE, but it's not enabled by default. To enable IMAP IDLE, open the Options dialog in
Gmail Notifier Pro and navigate to the Mail section. Check the setting Enable instant mail notifications (IMAP IDLE).
Read more about how to enable IMAP for Gmail and
the features supported by IMAP in Gmail Notifier Pro