Greetings riersonfamily,
Thanks for using the Apple Support Communities!
I understand that the Mail app on your iPhone is not functioning as expected and has been unexpectedly quitting. I can see that you have tried to restart the iPhone several times, but the issue continues.
To continue troubleshooting, I would simply add the one extra step of completely quitting the Mail app before restarting.
Force an app to close in iOS - Apple Support
After Mail has been closed, restart your iPhone again.
Restart your iPhone, iPad, or iPod touch - Apple Support
Once your iPhone boots back up, open Mail and test the functionality again.
Have a great day!