This error indicates the CSV file for the recipient list is corrupt. The file type may have originally had a different file type, was saved to CSV, but became corrupt in the process.
- Copy the content from the original CSV File
- Open a new CSV file and paste the copied content
- Save the file as .CSV
- Upload the CSV file to NetCommunity
- Create a New Email Template and Message using the new CSV File or use a message with a data source of None
- Copy the email message and try to send it again