Include a Tasks pane or Tab, similar to the Windows version of Outlook.
I sorely miss the Tasks pane from the Windows version of Outlook. This was such a messy, but useful feature that helped me organize projects and keep track of important emails. I would love to have this feature back on the Mac version. Having to switch between a Tasks tab (like Calendar) is not the same and less useful as I fall into the Out of Sight, Out of Mind trap.