When an incoming IM (or receipt for an IM you have sent) is received, a red icon flashes in the bottom of the contact window to the right of the Expiration display and also on the In Box tab itself. Click on a flashing icon or selecting the In Box Tab will take you to a list of incoming IMs and Voicemails. Each item in the list is a text or voice message and can be viewed or played back when selected. The content of the message can be seen in the lower part of the window. If a Voicemail is selected playback, stop and pause controls will be displayed and the message can be played back.
Right clicking on any item displays a menu allowing the messages to be managed. Options include, Save (to Mbox), Delete, Reply, Forward and Add Contact to add the message sender to your Contact list