If you send a monitored email to a contact and you receive a notification that they have already read it when should you call them?

–If you send a monitored email to a contact and you receive a notification that they have already read it, when should you call them?– —As soon as you receive the first notification.— –After I reply your email.– –After receiving at least 10 notifications.– –After receiving 3 or 4 notifications.–