I created a Rule to play a sound for each message received.
That still only played one audible alert per "send/receive".
I thought that was odd, as i expected multiple audible alerts.
I then set up a Rule to display a popup for each email message received.
That displayed one popup per "send/receive" with each incoming email listed in the popuup.
To me it seems Outlook is grouping things together in a "send/receive" in a way you don't want.
I have Outlook setup for several email accounts and account types (IMAP, MAPI, POP3).
Maybe it would work differently with a simpler setup...I doubt it, but who knows...
You could also look for a 3rd party tool that can do what you want.
Here is one i found you can check out: Mail Alert - Reclaiming your productivity, one e-mail at a time