Smooch.io for Facebook Messenger - Message your customers from Slack, Front, a bot or anywhere!
MailChimp - MailChimp is the best way to design, send, and share email newsletters.
GetChat.App - Add WhatsApp chat to your website for free
SendOut - Affordable email marketing for bloggers and influencers
Avochato - Text messaging for your business.
rasa.io - Get more from your email list.