1. A method comprising: authenticating, by a message routing system, an entity having an account with an application service provider; generating, by the message routing system, an authentication token for the entity, the authentication token indicating authentication of the entity by the message routing system; receiving, by the message routing system, a selection of the application service provider from a directory that includes a plurality of application service providers accessible via the message routing system; responsive to receiving the selection, transmitting, by the message routing system, the authentication token to the application service provider; directing, by the message routing system, the entity to the application service provider; and responsive to transmitting the authentication token to the application service provider, directing the entity to the application service provider, and the entity providing authentication credentials associated with the account to the applications service provider as part of associating the authentication token with the account, receiving, by the message routing system from the application service provider, a message indicating that the application service provider accepts the authentication token, the authentication token accepted by the application service provider as a substitute for the authentication credentials associated with the account.