Sometimes, when we have a formidable form filed out and a notification email is received by the website owner to their spam folder (and they miss the enquiry or lead) we have to check the settings of the Formidable Form email actions.
If after this has been adjusted on the form settings the emails are still ending up in the spam folder on the Office 365 system, then it may be necessary to adjust the the "protection settings" on the Exchange server.
If you have administration privileges on the Office 365 account, then you can adjust the malware protection and spam filter settings by following the moves in the video below.