Email Automations With Connected Boards

I am creating an inventory management system for my company. That system is comprised of a few different boards. For example, one for “kits” and one for “customers”. The kits board uses the connect boards column to associate a customer with the kit they purchased. I would like to create an automation to send an email to the customer when their kit has shipped. I am having issues doing this because the email is on the customer board and I can’t seem to utilize a mirror column to populate the email address. Does anyone have a thought on how to accomplish this?