I have been experimenting a bit with Google Apps.
Most impressive has been the email search capabilities and the ability to access my email anywhere.

Has anyone ever heard of being able to use GMail as the default mail client with Max 9?

Just set up Gmail POP access and read in Outlook or Outlook Express/Maximizer

When setting up Maximizer to communicate with your e-mail system it is important to understand what it can and cannot do.

In and of itself Maximizer possesses no e-mail capability at all, all the functions you see it do are managed by calling various aspects of your existing e-mail system through the MAPI.

So while you cannot set Maximizer up to communicate directly with GMail (as it has no POP client to manage the communication), you can setup a POP client on your machine to talk to GMail and then as long as the POP client is one of the e-mail systems Maximizer works with you will be able to access your GMail via POP3.