Does mass mailer within CB > User Management work? Test it by selecting a test users checkbox then clicking the mass mailer button. That typically only happens if the mailer function fails completely.

What mailer settings are you using within Joomla global configuration (e.g. smtp, php mailer, etc..)? Seams to be something wrong with either the mailer settings or the email in the account it self.

Strange, no idea what to suggest. PHP Mailer should be working fine. I don't see any issues with your settings. Best guess is the recipient email address is maybe causing issues. Have you tried other email addresses to see if those work? Do you have a different email configuration in AcyMailing that might explain why it works and CB doesn't? Does Joomlas mass mailer work? Also make sure you didn't disable CBs sending of emails within CB > Configuration > Integrations with the Send Emails parameter.