Hi Royvan,
First, I would like to confirm the relationship between the older server and the new server you mentioned. Are they two separated ones without any relationship?
Generally, if the DirSync deployed in the new server will also sync the Exchange users in the older server, we need to convert them to the MEU.
Otherwise, if the DirSync will not affect the Exchange users in the older server, there is no need to convert them to MEU.
Thanks,
Kid Yang
