Hello,
Respected Client,
You must have changed Nameservers when you have migrated from woocommerce to shopify.
It's related to DNS records as mail server is pointing to shopify or it's not defined at all. That's why aren't able to send and receive emails.
My task is to resolve email receiving and sending issue. I can't help you with email migration as you may have many email accounts associated with the domain so it will be a lengthy job. If you still have woocommerce hosting then I can help you to point current email server to woocommerce email hosting server and that's how your emails can start working again.
I need more information from you regarding domain of the website so I can trace current DNS settings of your domain.
I am waiting for your reply.
Thanks,
Best Regards,
NeOLiO