Can't send emails... "Failed to send test email!"

For some reason I'm not able to send test mail/emails.

"Failed to send test email! - Please check your outgoing email settings and server config to see if selected ports are open. Error details: The following From address failed: : Called Mail() without being connected"

I already signed up for mandrill and verified domain, I could use wpMandrill but just can't use the configuration on e-Newsletter.