To mark your messages read or unread you need to:
- Open your mailbox.
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- On mail list to the left, under the search field, click on the bulk option.
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- 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.
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- 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.)