Q: Ios 9.3 has serious email issues!

Consider yourself lucky that your iPad Air is not a brick. This is not Apple's finest hour.

If I were you, I would Contact Apple Support - AND - file a "bug report" from the menu choice on this form > http://www.apple.com/feedback/ipad.html

you're welcome (FWIW)

You are wise... millions of folk have been VERY adversely affected - I would wait a LONG time and keep checking the forums ( Using iPhone too ) for the "thumbs up" from US, not Apple.

iPhone which? It may be part of the "older device" Pausing from the 2nd one:

The "list" of pertinent articles as I know them to be as of now

- you can read about the problems in these articles, and possibly find workarounds, particularly in the last one

• If you can't activate your iPhone, iPad, or iPod touch after installing a software update - Apple Support
• Apple pausing iOS 9.3 updates for older devices, working on activation fix | iMore
• Apple releases new build of iOS 9.3 for users of iPad 2 affected by bricking bug | 9to5Mac 
• Apple Addresses GSM iPad 2 Activation Bug With Revised iOS 9.3, but Broader Issue Remains Unfixed - Mac Rumors
• If you can’t activate your iPad 2 (GSM model) after you update to iOS 9.3 - Apple Support 
• Troubleshooting iOS 9.3 Update Problems