Use the lcsk branch.
I'm currently building a completely free and open source customer communcation platform.
This is ambitious, but I've built two big SaaS in the last 2 years, LeadFuze and Roadmap so I'm confident about this one.
Website visitors (leads) and in-app signed in users can start conversation with agents.
When user are not online, they will receive the messages via email.
Create campaign based on user attributes, send email on key actions or behavior from your users.
This is actively in development at the moment.