can you let me know how can I export the contact who never recivied email from me. I can see 3000 emails sent out of 18K. I want to re upload only the 15 K.
You can export the email that is sent, then run the bulk update "Contacts->Bulk update" on the list and select the action "Delete Contacts". It will remove the sent email from the list. Here is the link https://support.mumara.com/help-center/articles/1/7/9/bulk-update of documentation.