"ExchangeGuid" is used by another recipient object

Hi,

I'm currently working with a wave 15 hybrid setup where we've run into a problem with one user account.

Error message:

Exchange: The value "xxxxxxxx-xxxx-xxxx-xxxx-xxxxxxxxxxxx" of property "ExchangeGuid" is used by another recipient object "". Please specify a unique value.

I get a conflict for the ExchangeGUID in Office 365 but not in the OnPrem environment. There are no mailenabled objects in 365 with this ExchangeGUID (I ran "Get-Recipient -Filter "ExchangeGUID -like 'userExchangeGUID'" without finding any conflicting entries). There might be another none mailenabled object i WAAD but I have no tools which will allow me to search or even retrieve the ExchangeGUID attribute for none mailenabled objects.

I could, of course, force a new ExchangeGUID for the user OnPrem (export and import all the mailbox contents) but it's not very userfriendly and definitely not a long terms solution if this happens to more objects.

Is there any way for me to search for or retriev the ExchangeGUID for all the AD-objects in  Office 365.

Regards

/Dan