Does anyone know if it's legal to send email through an open proxy in the United States providing there is no commercial element to the message?

For example... can I send as many emails to people as I'd like through proxys if I'm just saying hi?

If they are your contacts I don't believe there is a problem. If they are not subscribed to your e-mail list then it is illegal.

I thought that was only if you were sending commercial emails--something that promotes a product or website. I'm trying to find the specific legalities for sending personal emails.