Secondary email sender/provider

Mailgun is experiencing issues right now:

We’re experiencing an issue with a number of customer domains were incorrectly disabled. We are working to correct the rule that caused the domain to be disabled and re-enabling the domains.

The problem is new users can’t sign up because of this. They get the following error message:

Please enter a valid email address!

Would be nice that even if the mail provider is down, users could still be able to register. Or if there was a way to specify a secondary email provider in case the first one is down.