iPhone change over to 14pro

iCloud uses Apple ID credentials.

If you do not remember the Apple ID Password then follow the steps given in this Apple Article -> If you forgot your Apple ID password - Apple Support

If you do not remember the Apple ID then follow the steps given in this Apple Article -> If you forgot your Apple ID - Apple Support

If you are the owner or the owner has shared all information with you then to open Activation Lock:- If it is Activation locked, read here --> Turn off Activation Lock - Apple Support Activation Lock for iPhone, iPad, and iPod touch - Apple Support

Learn how to remove a device from a previous owner's account.

If you are not the owner and do not have the Apple ID and Password then there is no way that you can get into this iPhone unless the original owner shares the Apple ID and password with you. If you are lucky you can get into this iPhone if they (owner) accidentally remove the device from their Apple ID.

Restart the device. That's it. If issue is not resolved... Force restart iPhone - Apple Support

Which email account are you referring to? Google, iCloud, AOL, Exchange, Outlook, Yahoo or any Other

If you can't send email from the Mail app on your iPhone or iPad, there are a few things you can try.

...

Check the Outbox for unsent email

1. In Mail, go to your list of mailboxes.
2. Tap Outbox. If you don't see an Outbox, then your email was sent.
3. Tap an email in the Outbox. ...
4. Tap Send.

If you can't send email on your iPhone or iPad - Apple Support

Check Mail Fetch and Notification settings

To adjust these settings: Go to Settings > Mail, then tap Accounts. Tap Fetch New Data. Choose a setting — such as Automatically or Manually — or choose a schedule for how often the Mail app fetches data.29-May-2021

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