WhatsMany - Send personalised WhatsApp messages in bulk
Yac - Take your time back from Zoom & Slack
LoopMessage - LoopMessage is a perfect macOS tool for personalized mass messaging via iMessage/SMS, WhatsApp, Facebook Messenger, Telegram, Viber, and Skype.
Slack - A messaging app for teams who see through the Earth!
Porterhouse - Send mass iMessage and SMS texts from your existing number with a single click!
LinkedIn Voice Messaging - Communicate when you want, how you want