email="From: email@example.com\r\nTo: firstname.lastname@example.org\r\nSubject: tutor registration\r\n\r\n"+message
server = smtplib.SMTP('localhost')
server.sendmail("email@example.com", "firstname.lastname@example.org,email@example.com", email)
Look at the second to last physical and logical line and you note I have two emails to which I am sending the email message. My reading of the library doc suggests this is the correct format. In practice, it works only if there is one and only one to address. You might think sendmail needs configuring, but each of the above two addresses work individually.