Hi @MB35 ,
You can check the SharePoint Person Type Column's email address with the email addresses of excel using the Excel's "List rows Present in a table" by applying filter query.
//Excel Sheet:
I created the excel excel sheet with a single column table for list of email addresses. (Column Name = Email)

//SharePoint List:
I have created a List in SharePoint (Name = List1) and a Person type Column (Name=Users).

//Assumptions:
I am assuming that the flow will check the email addresses when a new item is created in the SharePoint List. So, I am using the SharePoint's Trigger - "When an item is created".
Power Automate Flow:
Added the " When an item is Created" in the SharePoint list Trigger and Added a Action "List Rows present in Table" of Excel to get the list of email addresses. Here if you noticed I applied Filter Query to filter the email addresses based on the email address added in the Sharepoint List's Column.
The Logic we are implementing here is - if the email address is found in the excel table, the flow "List Rows present in the Table" Action's Output Body/value returns that row otherwise return the Empty array ([]), if email not found.
Now, added a condition to check if the Output Values of previous Action ("List Rows present in the Table").
- If the email address doesn't exist in the Excel Table, the "IF YES" action is executed, and email will send to the Shared Email address.
- Otherwise, the if email address is found, "IF No" section is executed and the email will send to your colleague (as per the configuation).
//Here is the complete flow:

Now, Save the flow and test it by adding an item in the same sharepoint list.
//Testing:
For testing, I added two items in the list, and I received one email on my Shared Mailbox and other is on configured email address.

Please try this at your end and let me know if you have any question or face any issues.
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Thank you,
Harsh Deol