To delete messages in your Received or Sent box, click the More menu (represented by 3 dots) then click "Edit". Check the box next to each member whose message you would like to delete and click "Delete". You can also delete the message from individual member after reading it by clicking the More menu and then "Delete All". You will be asked to confirm your choice, click "OK" if you wish to delete all messages in the thread.
Deleted messages from your Received box will automatically go to your Trash box. Messages in your Trash will automatically be permanently deleted after 2 days. If you accidentally delete a message you want to keep, you can return it to your Received box by clicking "Edit", check the box next to the member whose message you would like to retrieve and click "Restore". Note that once you have deleted a message from your Sent box, you can't retrieve it.
All messages are automatically deleted after 2 months.