If two applications provide the same service (such as emailing your business card) then you can use the Application Services settings to specify which application should provide the service.
By default only services with multiple providers are shown. To show all available services select Show All Services from the Options menu.
To change the application that is used to provide a service:
When the list of applications that provide the selected service is shown the Details... item in the Options menu can be used to managed the all services and mime types provided by the highlighted application.