[qmailtoaster] Delayed delivery

[Raymond Webster]

I have one outside client that cannot send mail to the toaster. He is
sending from an Exchange2007 server. He gets a delayed delivery message to
the email addresses he attempts so send within our domain.
 
I have found this in the smtp log;
 
 CHKUSER accepted sender: from <[EMAIL PROTECTED]::> remote
<EXHUB016-1.exch016.domain.net:unknown:IPAddress> rcpt <> : sender accepted
 
Why would this make his server report a delayed delivery?
 
Ray Webster