What Sean said. This might help: http://www.sqlservercentral.com/articles/66909/

However with regards to #3, explain how the results are calculated. In your example, I assume you want "Customer123@provider.com", but you never say that. Or do you want another value?

What if there are multiple values in there? Or if this value is at the beginning? Do you only want the last email?

To try and help you code this, we need some better understanding of the rules under which you are operating.