A notification architecture utilizes multiple processes configured for managing notification operations based on reception of SMTP-based messages within IMAP based message stores. The notification architecture enables use of multiple instances of a notification process, each configured for receiving notification messages for respective subscribers from messaging sources according to a prescribed open protocol such as Internet Protocol. Each notification process accesses subscriber profile information from an open protocol-based subscriber directory based on the received notification messages. Each notification process determines, for each received notification message, the subscriber's notification preference based on the accessed profile information, and selectively outputs a notification delivery message according to a prescribed open protocol to at least one notification delivery process within the notification architecture based on the subscriber's notification preference. Each notification process may have access via the prescribed open protocol to multiple notification delivery processes, each configured for outputting a notification to a subscriber's notification device according to a corresponding device protocol. Multiple instances of each type of notification delivery process may also be utilized for increased capacity. Hence, subscribers may be notified of events according to their respective preferences, including subscriber device type, or time of notification. Moreover, the notification architecture can be scaled without adversely affecting any existing instances of the notification process or the notification delivery processes.