How to provide global functionality in multi-user database app

I have been building a multi-user database application (in C#/WPF 4.0) that manages tasks for all employees of a company. I now need to add some functionality such as sending an email reminder to someone when a critical task is due. How should this be done? Obviously I don’t want every instance of the program to be performing this function (Heh each user would get 10+ emails).

Should I add the capability to the application as a "Mode" and then run a copy on the database server in this mode or would it b开发者_StackOverflow社区e better to create a new app altogether to perform "Global" type tasks? Is there a better way?

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You could create a windows service/wcf service that would poll the database at regular intervals for any pending tasks and send mails accordingly.

Some flag would be needed to indicate whether email is send or not for a particular task.