iPhone supports Microsoft Exchange ActiveSync, delivering push email, calendar, and contacts for business. We get only one possible Exchange-account on our iPhone. With AddExchange (for jailbroken iPhones) you get the ability to add a second Exchange-account. Unfortunately you cannot add a third or more, only two accounts at most. AddExchange can be found through Cydia. After installation you push the plus-button in the application. Then you click on Settings > Mail, Contacts, Agenda > SRV2 and add the seconds account. AddExchange is compatible with iPhone OS 3.0 or higher.
You can delete at any moment, but you’ll have to wait until AddExchange 1.1 arrives. This version should be available any time soon.