I tested my SMTP out info in Thunderbird, and it works fine to send emails, but it won't send in eNewsletter.
The error I get is
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: (email address removed for privacy reasons) : Called Mail() without being connected
I tested this with all other plugins disabled except membership and the WPMUDev dashboard.