1. A method executed on a computing device for integrating functionality of a plurality of customer relationship management (CRM) applications/instances into an email, contact management, scheduling (ECS) application user interface, the method comprising: loading a CRM integration module in an instance of the ECS application; selecting one of the plurality of CRM applications/instances based on at least one from a set of: automatic selection and user selection; determining a context for the selected CRM application/instance; presenting a sub-user interface associated with CRM functionality related to the selected CRM application/instance within a user interface of the ECS application; querying a boot cache manager for a current sub-user interface configuration file upon start-up, wherein a Messaging Application Programming Interface (MAPI) data store within the ECS application queries the boot cache manager; managing states of the selected CRM application/instance and remaining CRM applications/instances through a state manager, wherein the state manager maintains a dictionary of CRM application/instance contexts and iterates through CRM applications/instances in the dictionary to evaluate a result of state determination for each CRM application/instance in each cycle; and in response to a selection of another CRM application/instance, activate a new instance of the state manager, update a state of a previously selected organization and the currently selected CRM application/instance, and retrieve configuration data associated with another sub-user interface, wherein each sub-user interface includes controls associated with actions related to the corresponding CRM application/instance.