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You can @mention a user using the Name or Login; whichever is unique. If there are more than one user has a similar nameusers matching the @mention, you will be presented with the user drop-down asked to pick the a relevant user. To view your @mentions, click on the @ icon in the menu. If you have unread messages, then a number appears in the top right-hand corner of the @ icon and indicates the number of unread @mentions you have.
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