Sending, receiving, and organizing email in Outlook.com
In my Microsoft account I designated a different email as a primary and removed my msn account. Since doing that I can no longer receive emails to that account. When I try to add it back it stats that the account is invalid.
What happened and how do I get it back?
If you removed an alias, it is now permanently deleted. See the first of the "Important" notices in the article at https://support.microsoft.com/en-us/office/add-or-remove-an-email-alias-in-outlook-com-459b1989-356d-40fa-a689-8f285b13f1f2.