I tried setting it up through Shopify and through Zoho Mail as well, but it's the same issue, I tried to send an email to that my domain email address from a different email but it says that the address doesn't exist?!!
If the email was created using Zoho, and the error indicates that the email does not exist, then I would recommend contacting Zoho Support for further assistance. To set up a Zoho email with Shopify, the MX records will need to be applied to the domain. If this is a Shopify managed domain, then you can add the DNS records in Online Store/Domains. More information on editing DNS records for a Shopify managed domain can be found here. If the domain is managed through a third party, then you'll need to contact their support if you're unsure of how to add the DNS settings.
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