The message could not be sent because the server rejected the sender's e-mail
address. The sender's e-mail address was 'firstname.lastname@example.org'. Subject
'test error code', Account: 'pop.penpublishing.com', Server:
'smtp.penpublishing.com', Protocol: SMTP, Server Response: '530 user must authenticate on this
port', Port: 587, Secure(SSL): No, Server Error: 530, Error Number:
This error means that the email account setting are not configured for smtp authentication. You must check the box in your account settings. Click here to for instructions.