When you or a colleague is notified in an email comment with an @mention,  you will receive the email in your Triage, with the newest email comment highlighted. You will then have the option to respond to the comment.

Any team members who are already part of the email conversation, or who have been brought into a comment with an @mention will be notified in Triage with all further activity on that email. 

If you do not wish to be notified of new comments, you can turn notifications off by clicking the notification toggle.

If the email is shared with your team (it appears on a public contact or work timeline), colleagues can turn notifications on for themselves, even if they aren't involved with the email conversation or comments.