- Must send/receive person to person messages
- Must allow rich text formatting
- Must support attachments
- Should have user presence detection
- Could have message retraction/deletion
- Could have user happiness analytics
- Must have the concept of group chats
- Must have dynamic group chat owner
- Must allow users to join/part group chats
- Should have historical log
- Should have historical log export
- Should have protected group chats
- Must have desktop application
- Must have web based interface
- Should have broadcast capabilities
- Should have mobile client (iOS/Android)
- Should have persistent data (encrypted server side)
- Could have external API for read/write events
- Skype
- Jaconda
- Basecamp
- Google Talk
- Google Plus
- Hall
- IRC
- SalesForce Chatter