Michael Rothwell has updated his excellent IMAP-IDLE plugin for Mail.app, which adds support to Mail for IMAP’s IDLE command , so that the server tells Mail.app when new mail arrives rather than Mail needing to poll the server.

This is obviously a much more intelligent way of handling the polling process.

The new version (1.05) contains a number of tweaks. It more reliably handles IDLE status messages and is smarter about detecting whether your mail server supports the IDLE command.

If it hasn’t worked for you in the past, it might now.

IMAP-IDLE is freeware and is available from Michael’s web site .

Michael Rothwell has written a plugin for Mail.app that adds support for IMAP’s IDLE command .

This feature allows the server to tell Mail.app when new mail arrives rather than Mail needing to poll the server.

As Michael explains,

It opens a connection for each IMAP account, selects the INBOX, enters IDLE mode, and waits for messages. When it gets a message from the server indicating that new mail has arrived, it causes Mail.app to check for new mail in that account.

The plugin will work with any IMAP4 mail server that supports IDLE, is freeware and is available from Michael’s web site .

UPDATE: Michael has knocked out an updated version of the plugin (1.01).

It fixes a small kink: “Certain IMAP servers (like Cyrus) were sending a reponse to the IDLE request that I wasn’t handling correctly.” Good news for Fastmail users (and others).

He also provides a link to a page with some info on which mail servers support the IDLE feature (dotMac doesn’t).

UPDATED UPDATE: Michael has produced another update (1.0.2) which (a) respects the “enabled” setting for individual accounts, (b) handles accounts being taken “offline” and (c) checks the mail server’s capability to support the IDLE extension and reports yea or nay back in the console log (see /Applications/Utilities/Console.app). Excellent!