After an upgrade to Exchange 2007 SP1 from 2007 RTM, the Xerox WorkCentre Pro stopped sending email scans. I originally thought it was an LDAP problem, because I had seen an LDAP error the night before and WireShark on the DC was showing the bind request but no other traffic. I finally resolved the Chimney problem with winpcap, but in the interim just used a port mirror on the catalyst.
Attempts to Email Scan on the WorkCentre Pro were throwing out an error page that said ‘Job Status: FAILED Job must have at least one “To:” recipient.’ Under the ‘Message Settings:’ header it listed From: with a valid address but the To: line was empty. Getting wireshark going showed that it was a 5.7.1 SMTP error and the Xerox just wasn’t communicating as much. Whitelisting the IP for the Xerox on the SMTP server resolved the problem.