The message could not be sent because one of the recipients was rejected by
the server. The rejected e-mail address was 'email@example.com'.
Subject 'test', Account: 'mail.hivelocity.net', Server:
'mail.hivelocity.net', Protocol: SMTP, Server Response: '553 sorry, that
domain isn't allowed to be relayed thru this MTA (#5.7.1)', Port: 25,
Secure(SSL): No, Server Error: 553, Error Number: 0x800CCC79
Our mail servers require SMTP authentication to properly relay mail. This
means that you will need to open the properties on your local email client
and enable this option. This is typically within the outgoing mail server
settings and you will also want to make sure it uses the same settings as
incoming. Below Is a Link to complete documentation on how to properly
configure your email client.