Closing this out as a duplicate, but if you still have issues after double checking your mail settings (particularly with a port other than 465 if your mail server does not support SSL/TLS) then feel free to open a new report.
Symfony\Component\Mailer\Exception\TransportException: Email to from failed: Connection could not be established with host "ssl://smtpserver.au:587": stream_socket_client(): SSL operation failed with code 1. OpenSSL Error messages: error:0A00010B:SSL routines::wrong version number