We are looking to find a best possible way to perform exchange attributes migration across forest. To share some background - Client has two AD forests, Forest A & B and both are in sync with same Azure AD. Forest A have all users identities(Account Forest) but no exchange servers and Forest B (Resource forest) has Exchange servers which are planned to migrate to 0365 and thus onpremises Exchange and forest B will be decom but we need exchange attributes on premises to manage mailbox properties. How do we achieve this?
one option could be migrate all exchange attributes from Forest B to Forest A using ADMT (Client does not own any paid tools like Quest) but I believe that would require exchange presence in forest A(since AD schema is not extended for exchange), is it possible to just deploy exchange management tools in forest A and then use ADMT to migrate these attributes or if this is not viable, please suggest what are the options do we have here.