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If "Mark items as read when viewed in the Reading Pane" and e.g. "Wait 5 seconds before marking items as read" is selected, messages are marked as read if you stay 5 seconds or
longer in the same message.
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If "Mark items as read when viewed in the Reading Pane" and e.g. "Wait 5 seconds before marking items as read" is selected, messages are marked as read if you stay 5 seconds or
longer in the same message.
...