An email ranking system assigns scores to emails of a user based on actions that other recipients of the emails have taken with respect to the emails. In determining the scores, the email ranking system may weight each recipient's action based on how closely connected the recipient is to the user and a type of connection the recipient has to the user. Each email's score may represent a likelihood that the email contains content that is important to the user. A client device may display the user's emails based on the scores. The client device may list the emails in descending order based on the scores, enabling the user to prioritize review of emails that are more likely to be important to the user. In this way, the email ranking system improves the client device by helping the user more quickly identify important emails.