I have an iPad Pro that I would like travel with, without having to take my MacBook. The limiting factor is that I have yet to find a way to reliably do email offline. I have tried Airmail, Outlook for iOS, Spark, and the native Apple Mail app, but none reliably downloads the emails and attachments. Airmail has a setting that purports to do this, but I have not found it to work. Has anyone found a way way to do this?