Report Suspicious or Incorrectly Classified Emails with Outlook
M365 now has self-reporting features to let Exchange Online and Exchange Admins to know when emails are not junk or should be reported.
Report Emails Incorrectly labeled
Outlook for Web
Use the connected app widget to report the message as not Junk. These actions should be enabled to your tenant by default. If you do not see them, please email us at ugmsupport@ugme.com
This is an improved feature from the usual process of right clicking the email and selecting 'Not Junk'
Outlook desktop:
Check your blocked and allowed sender's list:
Block senders or unblock senders in Outlook - Microsoft Support