Why is it important to use the EMProfileUpdate utility to modify client MAPI profiles?
Exchange Migrator 1.x
Exchange Migrator 2.x
It is always recommended that you use the EMProfileUpdate utility for redirecting MAPI profiles; however, some customers feel that their migrations are small enough that a manual update seems more logical for them.
If you decide not to use the EMProfileUpdate utility to redirect the MAPI profiles, it is very important that you do not manually modify the existing MAPI profile to point to the new target server. If a manual update is desired, a deletion and recreation of the MAPI profile is recommended to ensure proper profile functionality after decommissioning the source exchange server. The reason one might eventually experience issues when simply swapping out server names on existing profiles is that a manually modified profile does not update necessary registry mappings. Although the profile does in fact log on to the target mailbox, it still has registry references to the source exchange server which might make the profile nonfunctional after decommissioning the source exchange server.