Hi there and welcome
Can you tell me the error you get now on the Kindle please?
ok, then you need to remove and add the email account.
To do this, first remove it by doing the below
Open the Email app.
2. Tap Menu > Accounts.
3. Tap and hold the email account you wish to remove until a menu appears.
4. Tap Remove account and the account will be removed
Then to add it again select Menu > Add account.
Add your account to the Kindle and it should then start to receive emails again.
Let me know the results please
you cannot edit the send to Kindle address, you have to press the Menu, Add account and add a new email account.
The send to Kindle is for something else you cannot change.
Follow this film please, it will show you
Let me know how you go