An administrator account can connect to the advanced mode of the web UI, but not to the basic mode nor to the CLI.

Set the administrator account’s Domain to System. Domain administrators, also known as tiered administrators, cannot access the CLI or the basic mode of the GUI. For more information, see “FortiMail operation modes”.

If you require the ability to restrict the account to specific areas of the GUI, consider using access profiles instead. For details, see “Configuring access profiles”.