Hi @cutu234,
Thanks for reaching out! I apologize, but you can only send emails using your WP Mail SMTP authenticated email address. If you configure the Google mailer, you have the ability to send emails from your alias emails. You can learn more information here.
Or else, you need to authenticate your domain with domain based mailer (Eg: SendLayer, Brevo, SMTP.com) and then you should be able to send emails using multiple email addresses.
You can see all the available mailer from here.
I hope this helps. Thanks!
Thank you very much. Would be an awesome feature for the PRO version. 🙂