Twilio Flex - The programmable contact center platform 📱
WhatsMany - Send personalised WhatsApp messages in bulk
MessageBird Chat API - Connect with your customers through different messaging apps
LoopMessage - LoopMessage is a perfect macOS tool for personalized mass messaging via iMessage/SMS, WhatsApp, Facebook Messenger, Telegram, Viber, and Skype.
MessageBird API on StdLib - Purchase numbers, send SMS and more with one line of code
Porterhouse - Send mass iMessage and SMS texts from your existing number with a single click!