Hello Turtlewiz,
Thank you for using Apple Support Communities!
We understand from your post that you have changed your email account's password and cannot access email on your iPhone. If you are not prompted to enter the new password when you refresh the screen in the Mail app, then you may need to remove the email account and add it back again.
If you can’t send email on your iPhone, iPad, or iPod touch - Apple Support
"Remove your email account and set it up again
- On your computer, sign in to your email provider’s website. Make sure that all of your email is there or make sure that your email is saved somewhere other than your iOS device.
- On your iOS device, go to Settings > Passwords & Accounts.
- Tap the email account that you want to remove.
- Tap Delete Account.
- Add your account again."
Best Regards.