For BlackBerry 10 users with touch screens, open the BlackBerry hub, which displays your messages, slide your fingers together like a pinch and the €Pinch Filter€ will be applied. By default this filters out any read messages, but you can change how this filter works by going to Menu > Settings > Display & Actions > Pinch Filter Criteria.
To remove the filter, do the same movement in reverse.
To remove the filter, do the same movement in reverse.