According to the support page, it appears that MP Navigator EX is compatible with the following applications:
- Microsoft Outlook
- Windows Live Mail
- Windows Mail (Windows Vista)
- Outlook Express (Windows XP)
As you can see, Gmail is an unsupported service right now and only the developers can implement it into the MP Navigator EX.
I recommend to always stay updated with the latest released for your product via the Support page: https://www.usa.canon.com/internet/portal/us/home/support/