Sentinet is highly extendable through standard Microsoft .NET, WCF and WIF extensibility points, and thorough the Sentinet API interfaces. In the previous posts we saw how to build a custom access rule expression (standard .NET library) and how to leverage the WCF estensibility with a custom endpoint behavior. With this post I would like to continue the serie about the Sentinet Extensibility and demonstrate how to create a custom SMS alert handler with Twilio.