I need some assistance with troubleshooting the GroupWise Exchange Gateway.

I created a secondary domain for the Gateway and I'm running the MTA and
Gateway on the actual Exchange server (limited hardware).

I can send mail from the Exchange system and it goes to the GroupWise
system with no problems.

When I send mail from the GroupWise system to an Exchange user, the
Exchange Gateway reports:

ERROR (E01) 042027: Error submitting message to Exchange [80070005]

I've searched numerous message boards looking for an answer on this. I
created a special user and granted that user Exchange Full Administrator
rights. This user is NOT a member of the Domain Admins, Enterprise
Admins or the Exchange Domain Servers groups. (Microsoft locks these
groups down.) I DID remove the inherited rights from the Mailbox store
and granted this user Full Control of the mailbox store, including the
SEND AS and RECEIVE AS rights. This user is also part of the Local
Administrators group on this member server.

I've already exhausted enough hours trying to remedy this error, any
suggestions would be welcomed.