My accounts in mail settings are grayed out and I can not update my mail password on the phone or access icloud or calendars

Remove your email account and set it up again

Make sure that all of your emails are there or make sure that your email is saved somewhere other than your device. On your device, go to Settings > Mail, then tap Accounts. Tap the email account that you want to remove. Tap Delete Account.

If you can't receive email on your iPhone, iPad, or iPod touch ...

1. Is this your corporate iPhone? Then please contact the system administrator of your corporate
2. If it is your personal device, in that case, do you have any profile installed by your corporate/organisation/enterprise/School Management?
   1. Erase the profile added by you If you have installed a profile on your own --> Install or remove configuration profiles on iPhone - Apple ...
   2. Or please contact the system administrator of the organisation who provided the profile to you

You may have enabled Authenticator for Yahoo --> Generate and manage third-party app passwords | Yahoo Help