This article describes how to access and manage your blocked and safe senders lists within the Microsoft 365 Outlook Webapp
Sign into https://www.office.com/ using your SU credentials
Select Outlook from the list of available applications
On the right hand side select the gear icon to access settings then choose View all Outlook settings
In the settings window under Mail select Junk email.
Click Add below Blocked senders to add users to the blocked list or under Safe senders to add to the safe recipient list.
To remove an email address highlight the email to be deleted and select the trash icon to the right