Captive Portal with PW Emailed to Selected Domain

Hi Gurus out there. 

I'm trying to configure a 200D (5.6.8) to allow users to login to the captive portal by entering their email address (selected domain only) and pw that is emailed directly to them. 

Reason asking is to only allow staffs to use the use the wifi but to deter others. Unable to use AD-related authentication. My idea is for the captive portal to auto generate the pw and email it directly to the staff email address. 

Is this possible to do so at the given FortiOS version. 

Thank you in advance.