Zimbra - Zimbra is trusted by over 500 million users to increase productivity with a complete set of collaboration tools while maintaining total control over security and privacy.
Make It Rain - Random gifs when you get paid via Stripe (Slack and Hipchat)
Roundcube - Web-based IMAP email client
Darts Club: PvP Multiplayer - Darts Club: PvP Multiplayer is an amazing player versus player gaming app with a collectible twist.
iRedMail - A fully fledged, free email server solution, an open source project (GPL v2).
Red Stamp Cards - Red Stamp Cards is a fabulous mobile app that facilitates its users to greet their friends and family with excellent paper cards and notes.