Connection to us2.mx1.mailhostbox.com port 25 [tcp/smtp] succeeded!
220-us2.mx.mailhostbox.com ESMTP Postfix
ehlo test
521-5.5.1 Protocol error
521 5.5.1 Please see http://support.mailhostbox.com/email-administrators-guide-error-codes/ for explanation of the problem.