1. From the Edit menu, choose Preferences.So basically, you just reselect your SENT FOLDER in Preferences.
2. From the Mail & Newsgroups preferences category, select Copies and Folders.
3. You should see the Copies and Folders Preferences dialog box. Select where to store copies of your outgoing mail and newsgroup messages. If you don't want to use the default "Sent" folder, click "Choose Folder" to specify a folder location.
That does it.