Leopard’s Mail.app and IMAP Idle - never works quite right
I upgraded my home MacBook and work iMac to Leopard right when it came out. When I had Tiger, I installed an extention to Mail.app called “IMAP-IDLE”, which added support for the (logically named) IMAP Idle mode. This basically means that it will open an extra connection to your mail server, and when the mail server receives a new message, it notifies your client almost instantly. At work we have a Microsoft Exchange server, and for personal email I use gmail, and both were lightning fast - when I tested at work, I would see the new email in my inbox within a second of sending.
However, this behavior stopped when I upgraded to Leopard - it includes a built-in option to use IMAP IDLE, but it never seemed to work right - I would receive email only when I hit the “Get Mail” button, or my client checked on its specified interval.
I thought I had figured out how to make it work properly, it seems there are two settings that should impact this, but neither work well. Under Mail.app Preferences, under the Accounts Section, Advanced tab, if you select “Use IDLE command if the server supports it“, and you un-check “Include when automatically checking for new mail“, things work ok for a while. After making the change, restart Mail.app. However, if something happens, i.e. you close the lid on your laptop, lose the connection to the server, etc., it no longer works.
Why can’t apple get this working as well as the plugin was before? No good solution at this point…