Mail has been stuck at Upgrading your Mail database since the update to 10.11.1..

I'm on a Mid 2010 Macbook Pro... Everything was fine prior to this upgrade. The bar is stuck about half way through, and just stays. Everything shows the app as still responding. I've removed all mailboxes (all are stored online, so not worried about losing emails), and rebooted several times... Any help would be appreciated!

Thanks!