Thanks, this will always be a concern for these types of services. I will be keeping this service running indefinitely as I use it myself everyday along with friends and family. I originally created the service to solve my own problem.

The best way to mitigate against the risk of a service shutting down is to use your own domain name. That way, by simply changing your MX records to another email provider, you can continue to receive emails as normal.

Nevermind, it's all on github and seems pretty well documented. Great work!

That won't help though, as emails will still go to the old domain.

Which is exactly why you use your own domain so that you have the control.

The only way to prevent the issue you're describing is to use a custom domain.