Meeting created in GroupWise is sent to Outlook user and Outlook user accepts (or tentative/decline) the meeting invite. Response from Outlook is received by GroupWise Internet Agent (GWIA) and process properly. Moreover, Mail Connector processed the messaged correctly.
The owner of the meeting is a GroupWise user and the attendee is a user migrated to Exchange
However, the response from Outlook is never delivered to the GroupWise mailbox and bi-directional mail flows properly with or without Mail Connection in place.
Enable LDAP services under LDAP Settings on the properties of the GWIA gateway.