The easiest way to delete junk email is to first group like emails together.  You can do this by clicking on the Outlook mail bar. You can group emails by any of the fields on the bar. 

1.  Click on the field  (From, Subject, etc.), and Outlook will sort them in either ascending or descending order. 

2. Click on the first email in the group. 

3. Press and hold the shift key.  While still holding the shift key click on the last email in the group that you want to delete.  All of the emails between the first and last email that you clicked on will now be highlighted. 

4. Press the delete key to delete the email.  The emails will be sent to the Deleted Items Folder.  You then need to empty the Deleted Items Folder to completely delete these email messages.