After copying GroupMail Data from one PC to the other, on the “Sent Items” tab it shows “(message not found)” for every message.

This is due to the fact that the New PC has a different User Account Name than the Old PC.  To resolve this, simply close GroupMail.  Then, go to the C:\Program Files\GroupMail 5 Folder and locate a file called GMToolBox.exe  Double click on this file to launch it, go to Messages and press ‘Fix Paths’.  Once complete please open GroupMail and check your Sent Messages again.  All Sent Message should be displayed perfectly now that the paths have been updated.