Northern Trail Outfitters has Imported a file Into All Subscribers.

When Northern Trail Outfitters imported a file into All Subscribers and received a results file indicating that admin@example.com could not be imported, the likely error code that would appear in the file is B. List Detective. List Detective is a built-in functionality of Marketing Cloud that prevents the addition of email addresses that do not meet certain criteria to ensure list quality and compliance. It automatically blocks common role-based emails or improperly formatted email addresses.