You appear to be connecting on the wrong port. I am able to send via Office 365 using:
$transport = Swift_SmtpTransport::newInstance('smtp.office365.com', 587, 'tls')
->setUsername($emailUsername)
->setPassword($emailPass)
;
Obviously you would need to use the appropriate variables for username and password.
I do encounter regular 'submission rate exceeded' errors though even while using the throttler plugin set at 6.