Delete Gmail from Google Account

You can delete Gmail from your Google Account at any time. If you’re sure you won’t use Gmail in the future, please follow these steps to delete it:

Sign in to your Gmail account.
Click on your name or email address at the top of the page, then select Account settings from the drop-down menu.
In the “My products” section, click the Edit.
Click Delete Gmail Service and fill in the required fields. [source]