The Arduino email account can be changed from one email address to the another email address. Please make sure that, you are not logged-in with a Sign in with Google option from the Arduino log in page.
Below are the guidelines to change the email address of the Arduino account:
Go to the arduino.cc and sign-in to your Arduino account.
Click on your profile icon on the top right corner and select the profile sub-section.
You can change the email address from the change option as shown in the picture below.