Unable to map 'Assigned To User' of aha to 'Assigned To' field of ADO due is domain mismatch

Our organization has transitioned recently and so we got new domain for employees, currently both the domains are valid for employees. In few application like Aha! we have old domain itself, but in the new applications we are starting to use like ADO users are having new domain. When we are creating the integrating between Aha-ADO and trying to map user fields like 'Assigned To',etc. Integration is through error, as Aha is not able to find the user with that domain in ADO.

we are actually migrating from Rally [using previous domains] to ADO[using new domains].So, Replication of Rally<->aha integration is now going to be ADO<->Aha . All the integrations between Aha and ADO will be impacted because of this. for the whole organization.

Till the previous domains are removed, can we use aliasing, or any other solutions possible here !?