Hello @user317234 ,   The way our system works, if you're sending a single email to multiple lists, our system will only send the email once to contacts that might appear on multiple lists.   No, there is no segmentation or default contact field (first name, email address, phone number, etc.) for what file or method was used to add the contacts. You'd just need to create completely separate lists at that point, based on the file name, or create a custom field and have that info included in the file itself.   If you're wanting to segment your contacts in specific ways, see our main article on segmentation for the available criteria and ways you can further distill these contacts. ... View more