Trello - Infinitely flexible. Incredibly easy to use. Great mobile apps. It's free. Trello keeps track of everything, from the big picture to the minute details.

DM Pilot - The Easiest and Most Reliable Way to Send Automated DMs

Microsoft Planner - Microsoft Planner lets you easily bring together teams, tasks, documents, and conversations for better results.

Auto Message - Auto Message is a scheduling app that offers several features such as sending automated emails, automatically answering calls & sending SMS/text messages.

CAMPR - Open source project management tool with 16 modules

Auto Reply for whats - Auto Reply for whats is a bot that automatically replies to received messages, and you can also use its features to build campaigns for customer support.