Customers multiple email addresses

Question

I've been searching high and low but I can't seem to find any information on this. My client would like the ability of multiple email addresses to a customer, so that all sales emails would be sent out to a possible 2+ email addresses.

I know about customer fields, its the email side I"m a bit wary of.

Has any one got experience with this or have any suggestion on how to approach this?

Thanks