The Anti-spam features of this tool aren't perfect. You can help mark email as spam. This is from the FortiMail support (https://fortiguard.com/more/antispam).

Spam submitted will be analyzed, their signatures will be extracted and added to our spam signature database, which makes FortiGuard AntiSpam detecting and filtering similar spam. We appreciate your submitting spam samples, but do not respond to them because of the volume.

Submission Instructions:
For Microsoft Outlook:

  • Method 1:
    Open Microsoft Outlook
    Create a new email to submitspam@fortinet.com
    Drag the message(s) you want to submit from the "message listing" pane into the body of the new message window you just created.
    Send the message.

  • Method 2:
    Set Outlook to forward email as original attachment by
    In Outlook menu, click "Tools" -> "Options"
    In "Preference" tab, click "Email Options..." button in "Email" section
    In the drop-down section "When forwarding a message," choose "Attach original message text"
    Click "OK"
    From now on, you can simply click "Forward" button in Outlook and put submitspam@fortinet.com to "To:" address to submit a spam.