Watch Environments
Jira users can individually subscribe / unsubscribe to environments in order to receive e-mails, Slack or MS Teams notifications when environments are changed. Learn how to do it:
Subscribe to Environment Email Notifications
From Environment Details Page or Dialog:

On the Environment List Views, in the “Watchers” column, you can see the number of active watchers and decide if you want to “watch” or “unwatch” an Environment.

Each user can also subscribe/unsubscribe to Environments directly from the Environment Details accessible from the Issue Page:

Then, click on the watch icon on top right of the Environment Details:

Watching Options
To get only relevant notifications, a watcher can set different watching options for each Environment individually. He can choose to be notified when:
deployed version is changed
status is changed
environment is changed
an issue is associated to this environment (using an Environment Custom Field)
an issue is no more associated to this environment (using an Environment Custom Field)

Email notification examples
A new version is deployed
Example of automatic e-mail notification when a user is watching an Environment with deployed version is changed option activated:

A new issue is detected in DEV 1
Example of automatic e-mail notification when a user is watching an Environment with an issue is associated to this environment option activated:

Custom Emails, Slack and MS Teams Notifications
If you can also setup more advanced notifications using the Automation module: