Teem - Cloud-based meeting room booking system
Mailspring - Mailspring is a mail client for Mac, Windows and Linux.
BOOKMEETINGROOM.COM - Book Meeting Room - Conference & Meeting Rooms Management
Geary - Geary is an email application built for GNOME 3.
MeetingRoomApp - The best meeting and conference room booking system with a number of unique functions for effective meeting management and optimization of company processes.
Airmail - Airmail is a lightweight and lightning fast mail client for Mac.