The remote SMTP server can be tricked into relaying email, regardless of its relay configuration.
The remote host is running the MTS Professional SMTP server. This version of MTS is vulnerable to a flaw in the way that it handles malformed 'MAIL FROM:' headers. An attacker exploiting this flaw would send malformed 'MAIL FROM:' directives to the server. Successful exploitation would result in the attacker being able to relay traffic through the host.
Upgrade to version 22.214.171.124 or higher.