To send an email notification to a specific project collaborator, you can mention them in both revision notes and inline comments. When you type “@” symbol into the text box for either a revision note or a comment, you’ll get a list of project collaborators you can choose from.
Mentions will send notifications to the project collaborators you call out, even if their default email notifications are set to off. The notification they receive will say who mentioned them, content of the revision note or comment and a link to the project or file they were mentioned on.