I have a client who cannot send email to ONE specific address. When he tries, Outlook 2007 says;
Your message did not reach some or all of the intended recipients.
Sent: 11/02/2009 9:19 AM
The following recipient(s) cannot be reached:
xxxxxx xxxxxx on 11/02/2009 9:19 AM
None of your e-mail accounts could send to this recipient.
He emails plenty of other people just fine, and I can email the address in question as can plenty of other people.
His ISP assures him their mail server is not to blame.
Anyone have any guru ideas on what I can check to find out why this is happening?