External user cannot send email to one person in domain

[Hfnet]

My customer is running Exchange 2007 and Outlook 2003 clients. When one external person tried to send email in, it works to all but one user. The external person receives a 5.7.1 unable to relay on this one user and the email does not show in our EX2007 message tracking, but his emails to other users are fine.

Has anyone got any ideas on this, it is weird? The one user has no extra rights, is not a domain admin etc. All users are the same here.

Thanks.

 

[Zelandakh]

If you telnet to the Exchange server on port 25 "from" that person to your internal user, do you get the same 5.7.1?

 

[Hfnet]

yes, we get "sender ok" when we do MAIL FROM:, then "unable to relay" when we do RCTP TO: any internal recipient.

 

[Zelandakh]

Ooooh. And if you do MAIL FROM with your personal email address going RCPT TO your work address, do you get the relay error?