After migrating mailboxes with Notes Migrator 4.1, new items cannot be dragged int
o migrated folders that were created during the migration process.
This is caused due to a software bug in Notes Migrator 4.1, where a property is mis-set for any non-default folders that are migrated.
This issue is not present in versions of Notes Migrator other than 4.1. Furthermore, while items cannot be dragged/dropped, they can be moved by right clicking the item, and selecting "move to folder"
Waiting for fix in a future release of Notes Migrator for Exchange
Please contact Quest Support to see if an update is available that fixes this issue.