Thanks for this post, I had problems using SMTP with Mandrill and port 587 appended to the server, mail was sending from the mail test in Joomla but wouldn't send from CB including mass mail.
The Joomla mailer was using Mandrill and not php mail as a fallback, It was my servers firewall, opening port 587 solved the issue, and now both are sending.
Hopefully this will help someone.
Regards,
Andrew