The following error is received within the connector rallylog.log after configuring the <Emailer> in XML:
WARN : YetiMailer.initialize - Error sending email - 501 5.0.0 HELO requires domain address
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.