For a quick glance here is a video - Sending To Secondary Email in the client profile
Now the secondary email will also receive emails sent to all clients that were only sent to the original email.
If you'd like to receive an email on the secondary email, please ensure that the email is added under the Additional Email of the client biography.
To verify, go to SMS/Email under the Appointment head. Then under the "Send Email to Clients" section fill out the details of the client names, from email, subject, and message, and send the email by clicking on "Send Email".
Within seconds you will receive the email in your inbox.
Note: If both email ids are entered under the client biography then both will receive the email.