1. Get into the Junk E-mail folder.
  2. Select the email which you want to mark as Not Junk.
  3. Then go to the Home tab, click Junk and select Not Junk from the dropdown menu
  4. Alternatively, after selecting, right click on the emails, go to junk and then click “Not Junk
  5. After clicking Not Junk, a Mark as Not Junk dialog box will pop up, please check the Always trust e-mail from “xxx@xxx.com” box and then click Ok

Then the email will be moved to the original folder. And from now on, all emails sent from this sender will not be filtered to the junk email folder any more.