Systems Management

New to the community.  We just completed our cutover from on-premise Exchange to Office 365.  One big issue we've come across is that we are getting NDR emails with a DNS error for our Service Desk ticketing.  Our email address of servicedesk@kace.mydomain.com is set up as a contact in Exchange and was a member of our IT_tickets@mydomain.com.  People would email IT_Tickets with an issue and it would use the servicedesk email address to create the ticket.

Now that we're in the cloud, the online Exchange server doesn't recognize the servicedesk@kace.mydomain.com address and we get the bounced email.

Does anyone have any idea how to fix this?  By the way we are on an old version of the software - 5.4 and didn't renew support.  Gotta love budgets.