Slack is, where all information comes together. Monitoring (via Pingdom), updates for tickets and stories (via Jira), know-how (via Confluence), tasks (via Asana) and so on. For each of these services we have completely deactivated all email notifications. As a result, we receive only a very limited amounts of email and exclusively from clients and partners too. Internally, emails is a thing of the past for us.
Slack is therefore at the center of our organisation's software stack - and also our main communication channel. We communicate on a one-to-one basis or in groups via text, audio, and video, share each other's screens and can therefore work together comfortably from anywhere.