Mailtrain : Mailtrain is a self hosted newsletter application built on Node.js (v5+) and MySQL (v5.5+ or MariaDB). Mailtrain supports subscriber list management, ...
cal.com : Open source meeting scheduling tool. Send a link, let others book a slot. Calendly alternative.
SimpleLogin : With email aliases , you can be anonymous online and protect your inbox against spams and phishing. Open-source.
Garage : An open-source distributed storage service you can self-host to fullfill many needs.
Novu : The open-source notifications infrastructure. A fully-featured microservice to send SMS, E-mail, Slack and Push notifications. Embeddable notification...
A free, hosted, portable and open source photo sharing service. A photo application that lets you store your photos on Dropbox, Amazon S3 or in your garage.