Perhaps the following can be of help. Also excuse the wordiness - but believe the explanation is needed.
But first, this tidbit of information is important when trying to post a possible solution. When posting an issue, feedback, or request for help, it really is quite important to describe your computing environment. Because . . ., there are 6+ versions of Outlook apps and they do not share the same features or behaviors. Making this important to know what environment(s) you are operating in when you experience your issue or problem.
Here we go:
This reply will describe how to find the sender address of any email. However*, this works only in the following environments*.
Environment: Outlook app under Office 365 or Microsoft 365, running on a Windows 10 or 11 system. May work with Outlook.com but have not tried it.
Open Outlook. This assumes you are in the default Outlook orientation; a folder pane (inbox mail displayed), and the preview pane. Folder ribbon can be expanded or collapsed. Outlook window is NOT fully expanded. You can still see portions of your desktop.
Find the email you wish to know the senders address. Left click and hold on that mail item and drag the mail item to your desktop. You should then have a mail envelope icon representing the mail item.
Right click on the mail item (on your desktop), from the sub window move mouse pointer over the 'Open with' menu item. A sub-window should open listing various applications that can be selected. Select 'Word Pad'.
The Word Pad window should open to 'Home' and of course display a bunch non-sensible characters. On the Home ribbon select 'Find'. In the Find window type in 'SMTP' and select 'Find Next'.
Find will then show you 'SMTP:******@YYY.ZZZ where ******@YYY.ZZZ is the senders address.
Back to Outlook: Now that you have the senders address you can create a rule to handle that sender or domain. Or open Junk E-mail options and add it to your desired option.
Final Note: I do not believe that Outlook Rules are behaving correctly, under certain circumstances. Case: I have a rule that should automatically delete incoming email from specific senders and domains. The issue is that the rule does not run automatically and it should. The named senders or domains are treated as Junk email and placed in the junk folder.
I can select the Junk folder to see what is there and then open Rules, select the delete rule I created and the run the rule. The rule works and deletes 50-75% of the pure trash - spam and scam and unwanted emails. I keep my inbox email fairly restricted with other email ending in the Junk folder, which I will peruse at a later time. So, Outlook on iPadOS has a Focus and Other feature associated with the Inbox - that's kinda nice when trying to keep the onslaught of incoming emails somewhat organized. But same feature not available in Outlook/Office 365 on Windows.
P.S. Don 't forget to delete that email on your desktop. Drag it to trash.