I recently upgraded a GW7 environment to GW801 (running on OES2).
There is one secondary domain and GWIA still running GW7 on NetWare (soon to be phased out).
Everything went smooth migration wise.

The issue:
There is one External Domain an PO configured (lets say example.com) called Campus.INET (just so some users show up in the address book).
Everything worked/works fine when using the GroupWise 7 client (the client will be migrated later on).
So the user shows up as e.g. hein.konijn@example.com in the address book, the e-mail gets send to that e-mail address.
But when a GroupWise 8 client gets used it is mangled on the GWIA to "Hein Konijn.campus.INET@example.com" and a delivery error is received of course.
The odd thing is if the sent items is checked for that mail it says transferred to hein.konijn@example.com and just the icon of a delivered mail.

The user does receive an e-mail with:
Your message has encountered delivery problems
to the following recipient(s):

"Hein Konijn.Campus.INET"@example.com
Delivery failed
550 No such recipient

No recipients were successfully delivered to.

Is this a bug in the GW801 client or is it something else?