I`ve got GroupWise 8HP1 established, everything is working fine except periodic issue. One of users reports problems with sending emails but only to one domain.

The attached file had the following undeliverable recipient(s):

Information about your message:
Subject: subject
GroupWise Message Id: 4A7686C8.F07:31:30712
Message log tag: 242425
Number of send attempts: 5
Time of initial send attempt: 08-03-09 08:42:20
Time of last send attempt: 08-03-09 13:50:49

Transcript of session follows:
Command: pkopb.pl
Response: 450 Host down (pkopb.pl)

Does this in any case mean that the problem is on the remote host side? The strange thing is that pkobp.pl admin maintains that everything is fine with his server.