Organizing messages in a messaging system using social network information

A messaging system receives a message that is intended for a recipient, who is a user of a social networking system. An object associated with the message is identified based on the message content and/or metadata associated with the message. The messaging system accesses a social networking system database to obtain social information about a relationship between the recipient and the identified object. The message is then indexed using the social information, wherein an entry for the message is stored in a message index based on the social information. This process may be repeated for each received message, and multiple different message indexes may be generated for received messages to track different types of social information. A user interface for viewing messages uses the message index to organize the messages, such as to filter, categorize, and/or sort the messages in the display.