When migrating your mailboxes to a new server you can’t forget the ever important public folders. Public folders aren’t just for shared folders that you create on your own but they also include the required system public folders which allow Exchange to operate.
When migrating to a new server you absolutely need to migrate these public folders otherwise you will run into a whole host of issues on the new server and your users will be quite upset with you. Now you could just go to each public folder individually and setup replication, but that would take forever and a day, especially if you have tons of public folders.
Instead you should use a script called pfmigrate.wsf. It’s located in the exdeploy folder on your Exchange installation CD. This script will allow you to easily replicate the public folders to your new server and then after replication is complete you can easily turn off the replication.
Full instructions can be found here.