How can I register multiple emails for each customer in my wholesale shop?

[Xtrahunt]

Running a wholesale shop targeted merchants, I’m strongly in need of registering multiple email addresses on each customer. When receiving an order, I wanna sent an order confirmation to the default customer email. But afterwards I wanna send the invoice to another email address of the same customer.
How to handle such issue? Apps? Metafields?

[Jonathan-HA]

It seems Metafields would be a good fit for this use case.

You can create a Customer Metafield definition where the data type is “Single line text”. You can also add a form validation to only accept email address format in the metafield: