For authentication purposes, in some environments, you may already have Active Directory user security objects with no corresponding mail-enabled contacts. You are able to successfully complete the merge process and populate some common attributes such as givenName, sn, mail, proxyAddresses, targetAddress, etc.
However, mailNickanme attribute's value is not being populated. This value may be needed to sync mail-enabled user object once the merge process is completed to Office365 domain by Office365 sync agent.
On the other hand, if there is a corresponding mail-enabled contact or if you tell the tool to create the user if not found, mailNickname attribute's value gets populated.
STATUS
Enhancement request TFS266033 has been submitted to Development for consideration in a future release of GroupWise Migrator for Exchange.
WORKAROUND
Create corresponding mail-enabled contacts by using a script or Coexistence Manager for GroupWise and merge them with the Active Directory user security objects.
