Dear MikeStrada
Welcome to Microsoft Community.
Based on your description, you need to know how to find my blocked list issue on Outlook 365.
I would like to check with you if the block list you are referring to is an email blacklist list?
If you need to use blacklist as well as whitelist lists for email, you can turn them on as follows:
In Outlook, click on the “Delete” group under the “Start” tab, click on “Spam” and expand it, select the Spam option at the bottom, and then click on the “ Never block senders” button under In the pop-up window, click “Block Sender”, if you want to block certain senders or outgoing mailbox domains, you can add them.
If you want to block certain senders or outgoing mail domains, you can add them:Block or unblock senders in Outlook - Microsoft Support
Feel free to text back if you need further help.
Best wishes
Chris.S-MSFT | Microsoft Community Support Specialist