When you click on a thread, it automatically marks all of its posts as read.

In some cases you might want to manually mark some posts as unread—for example, if you open a thread but do not finish reading it.

Mark posts as read or unread

Do one of the following:

• Select Mark All Posts as Read from the thread's context menu to mark all posts in the thread as read without viewing the thread.
• Select Mark All Posts as Unread from the thread's context menu to mark all posts in the thread as unread.
• To mark individual posts as unread, click Mark Post as Unread from the context menu of the post.