Teem - Cloud-based meeting room booking system
Mailspring - Mailspring is a mail client for Mac, Windows and Linux.
AskCody - Meeting management system for Outlook & Office 365.
Geary - Geary is an email application built for GNOME 3.
BOOKMEETINGROOM.COM - Book Meeting Room - Conference & Meeting Rooms Management
Airmail - Airmail is a lightweight and lightning fast mail client for Mac.