I always recommend to use a third party, and I would recommend Intercom (http://www.intercom.io/). It has instant support service to have a conversation with the users. You can always use it to create automatic messages and emails to your users, even use segmentation for those messages.

I know Airbnb uses Mixpanel, but for metric purposes, to analyze their users and their actions, but that's not exactly support: https://mixpanel.com/case-study/airbnb/