If No Reply - Simple email automation that works for Gmail
Home-Assistant.io - Home Assistant is an open-source home automation platform running on Python 3.
Email Studio for Gmail - Send personalized emails, schedule emails directly in Gmail
ioBroker - flexible and modular application for the IoT and Smarthome
Boomerang Premium - Schedule email to be sent later, now w/ Premium features
openHAB - "empowering the smart home" - vendor and technology agnostic open source home automation