Add Alt Email as a Customer Field

Similar to the Alt Phone field, it would be useful to have an Alt Email field in customer accounts. There are countless customers of our who have multiple emails, either as individuals with multiple emails they'd like invoices sent to or companies that have more than one individual ordering for or interacting with an account who each have an email. If the alt email can also log into/order for the account, it cuts down on the amount of duplicate accounts created for the same customer company under different emails.