Question : SMTP 500 Syntax Error, Command Unrecognized

Setup: Native Mode Exchange Server 2003 Standard on a Server 2003 Standard R2 Box.  Running an IPCop Linux based firewall, using Appriver for inbound filtering only.

Today I have had 2 different users come to me because they are getting email kickbacks.  Those users have been trying to send to different users at the same outside company.  The outside company has confirmed that the email addresses my users are sending to are correct.  I have never run into this SMTP error before and am trying to figure out if this is something on our end or their end.  I would think their end as no other outside email addresses are encountering the same issue, or at least not yet.  Not sure what I should advise to the other company.  Any help would be appreciated.  When I run an MX lookup on my domain, it resolves to Appriver who handles all internal filtering.  No outside filters are used.  Any help or things to check would be greatly appreciated.

Answer : SMTP 500 Syntax Error, Command Unrecognized

Figured it out.  Simply had to change the property of the default smtp protocol, advanced delivery fully qualified domain name to read mail.richmonddiocese.org