Hello,
Please find the below article which will help you to block unwanted emails from your MSN email account.
https://support.office.com/en-us/article/block-senders-or-unblock-senders-in-outlook-com-afba1c94-77bb-4f50-8b85-057cf52f4d5e
For more assistance please follow the below link to contact the MSN Technical support team.
https://support.microsoft.com/en-us/contactus/msn/explorer-tech-services/
Thanks
MSN Support Team