Currently, if the connection to gmail goes down (mine said it needed to be refreshed), I get a very faint exclamation point above my name in the main navigation bar at the top.

When I hit send on emails within Nimble they appear to send.

When I view my sent emails box in Nimble, they show they sent.

However..... the emails did not actually send.

If my connection to gMail is down, I suggest that you do not allow me to "send" email until it's back online and put a great big red bar at the top of the screen alerting me to the problem.

CRM integration with email is pretty darn important. Important enough to raise hell about when it's not working correctly.