by the way, i have already checked the boxes TSL and SSL but the error persists...
i have tried to change the sendemail.py, adding a call to "smtp.login(username, password)" bellow of "smtp = smtplib.SMTP(serverURL)" ... and also failed.
Its quite an old post but i faced the same error a while ago-
It seems that if you use auth params within the email settings you should specify the server=yourmailserver:port parameter within your sendemail search command. The sendemail command uses the localhost on default.