a message appears under the field; fix the address.

Authentication-side failure

the error message appears under the field and the save stops.

Change your email address

Replace the email address associated with your account.

All signed-in users.

Being signed in and having access to the new email address (you'll need to confirm it).

Open the user menu, then My account.
In the Information section, edit the Email field. A help text reminds you that the change goes through a confirmation.
Click Save.
A message indicates that a confirmation email has been sent to the new address.
Open that email and click the link: the change only takes effect at that point.

Information section with the Email field and its help text.

Until the link is clicked

Your old email remains your sign-in identifier until you've confirmed the change from the link you received.

Invalid format: a message appears under the field; fix the address.
Authentication-side failure: the error message appears under the field and the save stops.