iPhone 2.0 firmware and IMAP IDLE
By chienr on Jul 28, 2008
The answer is still no, firmware 2.0 on the iPhone does not appear to support IMAP IDLE. The push email feature works only with Microsoft Exchange, MobileMe, and Yahoo!. If you go to Settings > Fetch New Data > Advanced, and select an IMAP server, only two choices are given: Fetch [periodically] or Manual. No Push. This is reaffirmed by my IMAP telemetry log. Just like in firmware 1.x, iPhone's mail client never sends the IDLE command.
Since I installed the new firmware on my original iPhone, I've noticed drastic battery life reduction. Following Apple's advice, I turned off push email and saw significant improvement. With push email enabled, I had to recharge it almost daily; now my iPhone can go 2-3 days between charges, which is still more frequent than, but closer to my experience on 1.x firmware.