Help!!! Mail Doesn't Work!

With upgrade mail won't run. I have g-mail based accounts for work, two volunteer organizations, a hobby account and personal email. Suddenly I can't do anything with mail!

I know there were some issues with Yosemite and g-mail but figured with all the talk about new 'stability' it would be ironed out and I could finally upgrade. Banging my head against the wall for trusting Apple on this one! <Arrrgh!>