Note in advance : If you have an E Delete my account All e-mails from this account will be removed from your Mac. In addition, you will also lose all settings related to the account. These could then only be restored via a time-machine backup.
How to Delete an Email Account on the Mac
If the email account is no longer needed, then follow Follow these steps:
First click on the Apple logo at the top left of the screen and then select "System Preferences" from the context menu. In the system settings, click on "Internet Accounts".
You will now see an overview of all e-mail, iCloud and other web-based accounts. E-mail accounts are usually labeled with an "@" symbol. Select one of your accounts to delete it. Now click on the minus sign below the listing.
You will be asked if you want to delete the e-mail account. Click OK". The e-mail account is deleted and you can exit the system settings.