In Dynamics 365 Customer Insights - Journeys, segments are based on attributes of Contacts or Leads, and CSV uploads to create segments just aren't directly supported. To include email addresses, import the data in the CSV first as Contacts or Leads using the Data Import Wizard, mapping fields such as email and name. You can also tag your imported records with a custom attribute, for example "CSV Import Tag," and then build a dynamic segment off of that tag. Otherwise, you could leverage a Static Marketing List in Dynamics 365 Marketing, which can import this CSV to a segment. Segmentation requires all email addresses to be existing Contacts or Leads.Kind regards,Sydney Digital Agency