Hi hldave,

Before moving on, I’d like to confirm your requirement:
1. You want to stop receiving emails from MSNBC.
2. Do you reach your email account via Outlook client or OWA?

If this is the case, please follow steps below:
If you connect your email account via Outlook 2010:
1.Click on "Info" and choose the option for "Account Settings." On the new tab, click on the option for "RSS Feeds."
2. Scroll through the various feeds you are subscribed to and locate the feed for MSNBC. Select the MSNBC feed and click the button to "Remove." The feed will then be deleted from your Outlook account, stopping the emails from entering your inbox.
If you reach your email account via Outlook Web App, you can set an inbox rule to move the MSNBC emails to junk folder.
Sign in from here: mail.office365.com
HOW-TO:

Thanks,
Robert Li