Robert Chien's Blog

To facilitate push Email to mobile devices? I'm doubtful, here are the reasons:

First, IMAP IDLE relies on keeping the IMAP connection alive. Mobile devices are more likely than desktop clients to experience network errors and timeouts as they travel. And devices capable of both Wi-Fi and cellular, like Apple's iPhone, automatically switches from one network to the other, terminating the connection as they do so. I feel that a true push solution should not depend on a persistent connection.

Second, an IMAP IDLE session only monitors a single mailbox. If you need to watch multiple folders simultaneously (like if you use server-side filtering or subaddressing), you need multiple sessions. Is any client capable of that?

Third, maintaining the session not only drains the battery, of which mobile devices have limited amount, it also hogs the data channels so I don't think telcos like that idea very much.

Michael told me OMA-EMN uses sideband SMS for notification, so it's designed to be friendlier to battery and network operators compare to IMAP IDLE. But I've yet to come across a client that supports OMA-EMN.