What is happening is that the <Emailer> is sending your internal system name for Sendmail. The remote server performs a reverse DNS lookup and rejects your HELO as an invalid domain name.
Resolution
First check the hostname of the connector system and ensure that it is valid:
Improper Hostname: example
Proper Hostname: example.domain.com
The address referenced should be a fully qualified name known in DNS. If such a name is unavailable, a domain literal should be used, again for the sending system.