I had exactly the same problem, namely I was going to send a mail with some attachments (6MB pictures ) and then black out, mail was probably frozen, tehn closing and back to the starting page of iPad. After that every time mail app starts meant showing a white page with some icons, but no content, then black page and closing the app.
After reading what others did in such a case: reboot iPad, send the critical mail/delete from my gmail account from other PC, later delete only gmail account (the last mail causing the crash was sent from there) from my iPad, restore iPad by a two month ago status (unfortunately i lost only some notepad messages and other staff, but mail was not recovered!!!) In the meantime the Gmail app was newly installed on my iPad and functioning perfectly!! Also i updated to ios 8.3 after crash, but no help.
Last chance was to delete all of my accounts (i had 5 different ones) and suddenly mail started to show something... Namely at the next start asking for account offering the account starting page . Then i reinstalled firstly my gmail account succesfully via running mail app and instead of new account downloaded actual mails from the server the original status of the account came up with the unsent big email attachments etc. Then i could simply delete this draft, close the mail app and install the other accounts without any problem. Now mail is functioning like before.
Hope it helps you and others as well.