email support as it comes out of the box just sucks, Forget about it.

It does not do imap idle,
Nokia messaging does not work from many places and costs money in others and cannot be configured properly.

Easy debian provides you with a simple unix machine with great email clients like

Thunderbird (called icedove) which supports imap idle but is a bit heavy on the n900.

The configuration i'm using is

gnubiff on top of easy debian does imap idle and can run any command when you get an email.
The command I use is sylpheed --retrieve.

Sylpheed is a great small and lightweight email client.