Email based two-factor authentication, Fortimanager

Hi,

I have got a VDOM and it is managed by  the Forti-Manager, not with Fortigate GUI. I am looking to implement two factor authentication for my SSL VPN users and suggested mechanism is using email to deliver the token.  But I cannot find the place to configure SMTP server information. I have found guides but all of them are describing the process on Fortigate not using Forti-Manager.

Please help me overcome the issue.

Thanks

TBK