I had this same problem under GW v7.0.2hp1 (see the GW7 GWIA forum on
06-18-2010), and I am now unfortunately having it on our newly upgraded
GW v8.0.2 system.

Our system config is as follows:

NetWare 6.5 SP8 (patches are up to date)
GroupWise 8.0.2
No third party directory processing is involved (i.e. - GWAVA, etc.).
No anti-virus scanning the domain or post office directories.

Here's the problem:

The GWIA will periodically (twice in 5 days this week for example) have
a rash of "Recipient is undeliverable" errors in the GWIA logs. This is
occurring to INCOMING e-mails, sent to legitimate/correct addresses.
When this occurs, those incoming e-mails are not delivered, and the
sender gets a "550 No such user" error response. If the sender resends
the original message, sometimes requiring multiple attempts, it will
eventually go through. I had 96 messages not get delivered over a three
hour period this morning because of this issue. I can make the issue
stop after a restart or two of the GWIA, but then it occurs again a
couple days later. I'm getting a number of complaints.

A GWIA log excerpt follows below, showing the behavior as it started
this morning at 6:07 AM. Other than my own post in the GW7 GWIA forum,
and the responses to that post, I can't find any other information
regarding this.

I did notice the problem seemed to start just as one of my users is
being spammed from several sources within a short time. I'm wondering
if the SPAM e-mail was crafted in some specific way in an attempt to
break the GWIA (well, the target was more likely an Exchange server).
Not sure that knowing that helps to troubleshoot this in any way.



*********** GWIA LOG EXCERPT ***********

06:07:34 03D MSG 77167 Processing inbound message:
06:07:34 03D MSG 77167 Sender: info@dizdarybound.com
06:07:34 03D MSG 77167 Recipient: df@ourdomain.com
06:07:35 051 MSG 77165 File:
SERVER\VOL:\GRPWISE\WPGATE\GWIA\wpcsin\4\4cdb8827. ad0 Message Id:
(4CDBCE76.CA8:56:19624) Size: 21.8 Kb
06:07:35 049 MSG 77166 Queuing to MTA
06:07:35 049 MSG 77166 File:
SERVER\VOL:\GRPWISE\WPGATE\GWIA\wpcsin\4\4cdb8827. ad2 Message Id:
(4CDBCE76.CA9:57:19625) Size: 11.7 Kb
06:07:35 03D MSG 77167 Queuing to MTA
06:07:35 053 MSG 77168 Processing inbound message:
06:07:35 053 MSG 77168 Sender: info@somnusterran.org
06:07:35 053 MSG 77168 Recipient: df@ourdomain.com
06:07:35 03D MSG 77167 File:
SERVER\VOL:\GRPWISE\WPGATE\GWIA\wpcsin\4\4cdb8827. ad4 Message Id:
(4CDBCE76.CAA:58:19626) Size: 12.7 Kb
06:07:35 03D MSG 77169 Processing inbound message:
06:07:35 03D MSG 77169 Sender: info@somnusterran.org
06:07:35 03D MSG 77169 Recipient: df@ourdomain.com
06:07:35 053 Recipient is undeliverable
06:07:35 053 MSG 77168 Converting message to MIME:
06:07:35 053 MSG 77168 Queuing message to daemon:
06:07:35 053 MSG 77170 Processing inbound message:
06:07:35 053 MSG 77170 Sender: info@somnusterran.org
06:07:35 053 MSG 77170 Recipient: df@ourdomain.com
06:07:35 037 DMN: MSG 77171 Sending file:
06:07:35 03D MSG 77169 Queuing to MTA
06:07:35 03D MSG 77169 File:
SERVER\VOL:\GRPWISE\WPGATE\GWIA\wpcsin\4\4cdb8827. ad6 Message Id:
(4CDBCE77.CAC:60:19628) Size: 11.7 Kb
06:07:35 053 Recipient is undeliverable
06:07:35 053 MSG 77170 Converting message to MIME:
06:07:35 053 MSG 77170 Queuing message to daemon: