If phpmailer works then Joomla is likely falling back to it. Joomla does not error when SMTP fails unless it's an authentication error. You likely have a certificate error. The SMTP certificate hostname likely does not match what your host is having you supply for the SMTP hostname. See the below for a similar case. CB does not fallback in the event of any error or validation warning on purpose so you know what's configured wrong.

www.joomlapolis.com/forum/147-potential-bug/236007-confirmation-email-not-working?limitstart=0

Latest CB build has the lasted PHPMailer class, which handles emails (SMTP, sendmail, etc..). Ours is more up to date than Joomlas, which either doesn't have the certificate verify (and will when they update), Joomla has turned off the verify (I hope not), or it's just silently falling back to phpmailer (likely what it's doing).

Could it be because of a beta version? or maybe because of a config in cb that i did not filled?

We don't have a beta version. Our builds are as stable as stable releases. They're all tested the same.