Delete Messages in Get Mail

  Double click on the Options Icon on the top toolbar.
  Click on Deleting & Moving Messages under the Message Options heading.

  Place a Check Mark in “When deleting messages, move them to your Trash
  folder instead of marking them as deleted” option.
  Click the Save Options button.

  Go back to your Inbox by clicking the Inbox icon located on the top toolbar.
  Place a check mark next to the messages you wish to delete and then click the
  “Delete” option located above or below your messages.
 

  Go to the Open Folder drop down box located in the top right corner and choose
  the Trash option. This will show you all your deleted email messages. If you want
  to permanently delete these messages you can place another check mark in the
  boxes located to the left of the messages and then click the Delete option.

  To change when your Trash folder messages are automatically deleted go to
  Options, Login Tasks and change the "Purge Trash How Often" to
  the desired setting (every login, daily, weekly, monthly, or yearly).