OK, it's all clear now. You have a name resolution problem.

Apparently smtpout.secureserver.net is not a valid hostname, and the
proper fix would be of course for those who manage that server to fix
their broken dns records.

A workaround on your end could involve the use of brackets, but simply
putting an unresolvable hostname inside brackets does not fix the
problem - the hostname is still unresolvable.

What you need inside the brackets is the IP address of the server.