A bridge, by definition, is the entry point to the Tor network. As such, the exit policy, which will allow traffic to exit the Tor network from the server, should be the following:

ExitPolicy reject *:*

This prevents your server from running as an exit node. If you do decide to run an exit node, be prepared to receive some complaints from your ISP if you are running it on a home network. This is why the Tor Project and the Electronic Frontier Foundation recommend that you don't run an exit relay on a home network. A thorough, legal FAQ prepared by the Electronic Frontier Foundation can be found at https://www.torproject.org/eff/tor-legal-faq.html.en.