You have the option to search through your Inbox by typing keywords into the search box and clicking Search. In the example below, the keywords 'Social Media' were typed and the messages below the search box contain the words 'Social Media' in the message.

You also have the option to filter messages by checking the box on the right of the service you wish to view. In the example below the Facebook Fan Page 'London Daily Deals' was checked. This means that only messages relating to this Facebook Fan Page will be viewed.
