Google Spreadsheets and MailApp.sendEmail

I need to perform mass mailing via Google Spreadsheets. The code itself works, however, when I try to call the UDF I coded in Google Spreadsheets, it responds that I have no permissions for the method despite the fact my Google account has required permissions for the script to run (thus allowing it to perform test runs from App Script).

Exception: You do not have permission to call MailApp.sendEmail. Required permissions: https://www.googleapis.com/auth/script.send_mail (line 12).

Must I set Google Spreadsheets permissions somehow?

Thanks in advance for your assistance.