An association server in a communication system receives a device identifier of a user device and searches a device-to-token database in order to determine whether the device identifier is currently associated with any device communication token. In response to determining that the device identifier is associated with a device communication token, the association server creates a communication account for the user device on a communication server, and sends a login credential for the communication account to the user device in a message transmitted via a message server. The message is addressed by the device communication token to a predetermined application installed on the user device. The predetermined application on the user device receives the message from the message service, and thereafter automatically logs in to the communication server according to the login credential included in the message.