03/20/2018
Is your iPhone mail app crashing when you try to open it?
I could not find the answer to this problem anywhere, but this is the solution that worked for me.
1. Delete the mail app. DO NOT log out or delete ANY mail accounts, just delete the mail app.
2. Reinstall the mail app from the iTunes store.
3. Before opening the newly installed mail app, go to Accounts and Passwords under the settings and turn mail back on any account that you had it on before the reinstall. (When you deleted the mail app it turned off mail on all these accounts.)