When you have an unread message from a contact in a chat conversation, a red icon with the number of unread messages is displayed to the right of the contact’s name in the conversation pane.
Unread group messages are indicated with a red outline.
Additionally, a badge is displayed next to your system tray icon that indicates the number of unread messages.
Depending on your notification settings, a pop-up notification may also display when an incoming message is received.
Click the notification or contact or group’s name to navigate to the conversation and view the unread message.