Previously the master user details were not included in the list of users under Setup > Users. The master user is the first username and password created when the account was created, and has full access permissions. As such, this is typically held by the account owner.
We have now included the Master user in the list of users in the account and you will be able to see the username and linked email address for the master user in this section. This is to help to be more transparent with who the master user is and make it clearer how to update the master user details.
We still recommend that the account holder is the master user, as the master user has full access permissions in the account
Only when the master user is logged in will they be able to update the username, password or email address of the master user. No other users will be able to edit these details via the Setup menu.