As someone tweeted this morning..."Do not panic. Back away from your desk and go outside for 30 minutes." Good advice but Google is saying check back in a couple of HOURS!! - OK, NOW you can PANIC!
Apple Mail caches mail from Google, so anything up to the time of the outage is stored on your local computer. As soon as service is restored, Apple Mail will refresh and download all the mail since the outage.
In addition, you can still write emails, they will just sit in your OUTBOX waiting for the GMail service to be restored.
I'm a real NUT when it comes to redundancy. I recommend that you have a backup email account for absolutely critical email messages.
In fact, even today, personal GMail was working. It was just the Google Apps program that was down.
I also have a Hotmail, Yahoo and a bunch of email accounts with some personal websites I have. OK, maybe I have too many - because I have more than that, really. POINT IS - I can still communicate if I need to.
But, honestly, I'm going to follow that "tweeter's" advice and just calm down and wait for service to be restored!