Why make it so complicated?
There is no need to have people send you their email address. All you need is a button on your website, which when clicked sends you an email from the email address that clicked the button.
When you receive this email you just add the address to your address book. All local mail clients (even most Webmail clients) have the option to do this either manually or automatically.
If all these people are going to be receiving the same email from you then you get your email client to add these addresses to a Group Account. That way you only mail the "Group".
CAUTION: Make sure that you set up your group mailing so that the reciepients cannot see the other reciepients email addresses. You will have a lot of unhappy people - and probably a lawsuit - to deal with.