The process in which email recipients send your message to people they know, either because they think their friends will be interested in your message or because you offer incentives to forward messages. Forwarding can be done through the recipient's own email client or by giving the recipient a link to click, which brings up a registration page at your site, in which you ask the forwarded to give his/her name and email address, the name/email address of the person they want to send to and (optionally) a brief email message explaining the reason for the forward. You can supply the wording or allow the forward to write his/her own message. AKA viral marketing.