Acompli - iPhone email just got a promotion
Stork.ai - AI-Based Collaboration for Hybrid Teams. Rich media messaging, advanced video and voice conferencing, auto-transcribing and screen sharing. Serendipitous meetings at the water-cooler with your human and AI teammates.
Send - Instant messaging meets email (by Microsoft)
Tatsu - Standup meetings for remote teams.
Brosix Instant Messenger - Secure instant messenger for your team
openmeet - Account free video conferencing with a rooms component that lets you use VC within a physical meeting room. The server can also be hosted in your own cloud for extra privacy/security.