Re: Push email for mobile?
The plan for next week, so far, is to go through the config for spam and virus filtering (the original plan was to do it all in this part, but I felt I'd have to compress things so much it wouldn't be helpful).
In terms of notifications, a few things come to mind off the top of my head, at least as far as Android is concerned.
Firstly, choose your mail client. For example, MailDroid has a various options to control polling, including control over whether or not connections are maintained when you exit a mailbox, and whether or not mail should be checked when the device is asleep. For me, that's fine.
Secondly, you can sign up with Google to send notifications over their network to Android devices via GCM. It's quite easy, having registered for that, to send messages from the command like, for instance via a PHP script or curl.
So, in terms of getting notifications out, you could use a Procmail recipe to send a push notification for new messages.
On the client side, I'd then knock up a very simple listener to register with GCM and display the notifications, and start the mail client if required.
If you don't want to do any coding yourself, you could use something like PushOver.net to deliver notifications, though it's not completely free.