Telegram - Telegram is a messaging app with a focus on speed and security. It’s superfast, simple and free.
Lotame - Make your data actionable, learn about your most valuable customers, improve ROI by targeting the right audience and increase relevance across screens.
WhatsApp - WhatsApp Messenger: More than 1 billion people in over 180 countries use WhatsApp to stay in touch with friends and family, anytime and anywhere.
Adobe Audience Manager - Adobe Audience Manager is a data management platform that integrates online and offline data to deliver a unified view of all your audiences
Facebook Messenger - Facebook Messenger is a faster way to message.
Google Audience Center - 3 votes and 6 comments so far on Reddit