This issue typically applies to users who took advantage of "Send & File" feature in Lotus Notes which enabled users to save a copy of the sent message in both Sent folder as well as another folder of user's choice. Also, in Lotus Notes it was possible to file a single copy of an e-mail message into multiple folders. The "Move to Folder" dialogue box included two buttons: "Move" and "Add". The "Move" button would physically move a copy of an e-mail message from one folder to another, for example from Inbox to any folder. The "Add" button would make the same message appear in two (or more) separate folders, for example Inbox and any other folder.
In Outlook, it is not possible to have an e-mail message appear in more than one folder. Therefore, all copies of sent messages would only appear in "Sent Items" folder after the migration, even if they were filed in other folders in Lotus Notes while being sent out. Also, messages stored in Inbox folder would no longer appear in any other folder that they may have been added to in Lotus Notes.
This is a limitation of Outlook software for which currently there is no workaround.