Step 1: Login to your Sandbox Account.
URL to login: https://test.salesforce.com/
Step 2: Click your profile avatar (top right corner) and select Settings.
Step 3: You will be directed to the “Personal Information” screen.
Step 4: Navigate to the Email field, enter the new email address ([email protected]), and click Save. A confirmation message will appear indicating that a verification email has been sent to the updated address. Click OK.
Step 5: You will receive a confirmation email on your Admin email address. Click on the confirmation link to update the email address.