Hi

I have to do a cross forest migration of Exchange 2010 to Exchange 2013. The users are already working on the new domain but still connect to the mailbox on the old domain.

Unfortunately the accounts where not migrated using admt, but they were synchronized using a third party tool, so there is no sid history.

Now I have to migrate the mail data. Is it possible to do a remote move and tell the request to which target mailbox the data should be moved?

Or do I have to export the data to pst files and import them in the new environment?

Regards
Peter

Hi Peter 

This can be done with the legacy exchange DN value

you simply take the legacyExchangeDN from the user in the source domain:
/o=Org/ou=First Administrative Group/cn=Recipients/cn=username


Go to the user in the destination domain and use for example ADUC (with View -> Advanced Features) and Attribute Editor tab. 
Go to proxyAddresses and add a value starting with x500:<legacyExchangeDN>:

Beside the above suggestion, you may also follow this informative KB that could be a good start-up for you. It covers almost all the required aspects and provides step-wise instructions to accomplish this task : http://msexchangeguru.com/2013/11/03/e2013crossforestmigration/

Moreover, if you wish to achieve this goal automatically, you may also consider on this automated software (http://www.exchangemailboxmigration.com/) that could be a good alternative approach for you and get this job done in more hassle-free manner.