To mark your messages read or unread you need to:
- Open your mailbox.
- On mail list to the left, under the search field, click on the bulk option.
- Then you can select all the messages that you intend to mark them as read or unread.
- Then choose mark as read, or mark as unread.
- You can also choose to delete your mailbox history. (Please take into consideration if you chose to delete your mailbox history there will be no way to restore that again.)