Boxer has been my default email app for a couple years now. I've found it much more stable than Mailbox. I have very large error-log reports for our in-house product, only Boxer can handle them:) Today they rolled out a big update introducing calendar&contacts support meaning it's going to be way easier to schedule meetings on the phone. Better Apple Watch notifications are also in the update! More about the release here: http://www.getboxer.com/introduc...
I have tried seemingly every email app out there. Astro. Outlook. Airmail. Notion. I always return to Boxer. It is a stable, dependable email app. It lets me apply multiple labels to an email. It is fast, clean and powerful. So good!