LinuxQuestions.org - did not issue MAIL/EXPN/VRFY/ETRN during connection to MTA

We have a phone system (not VOIP) that uses our mail server as its smarthost to email voicemail attachments. In Exchange 2007, I configured a send connector to let this host relay to domain users. That all worked fine.

We recently switched from the Exchange server to sendmail on linux which has the Exchange server host set as the smarthost.

Email is flowing fine from the Internet through sendmail to the Exchange Server host; except for email from the phone system. The /var/log/maillog has the following error:

Apr 10 00:28:49 webserver sm-mta[12529]: r3A4Sioj012529: host-66-202-79-114.roc.choiceone.net [66.202.79.114] did not issue MAIL/EXPN/VRFY/ETRN during connection to MTA

I have both this IP and domain name set in /etc/mail/access:

66.202.79.114 RELAY
choiceone.net RELAY

that doesn't seem to help. I've seen this "did not issue ..." message all over the Internet and it appears to be somewhat of a catchall error.

This worked quite simply with Exchange, I hate to say. I've always favored Sendmail. What am I doing wrong here? This issue is my top priority at the moment so any help or ideas would be greatly appreciated.

I've seen lots of posts all over the web on this, but no solutions.