Follow Subscriptions for Work and Issues
Follow subscriptions allow you to receive email notifications whenever any change is made to a work item or issue. This includes new notes, file attachments, table updates, status changes, etc.
Follow subscriptions work on a one-to-one basis with work items and issues, but they can be turned on and off in bulk.
You can follow issues by checking the Follow option on an issue details page, or on the main Issues > Summary page.