email invitation
What you may want to do is go through your own personal email and anything that gets sent to you from companies, such as LaCie, LL Bean, etc usually have the answer you are looking for.
Most companies actually set up a webpage that has all of that information built onto it, and then the email that is sent out simply just has an http: link that that page embedded into the email so that once the person opens the email, and obviously there is an internet connection, the page will automatically direct itself to the http: link and grab that page.
I've done one before, but unfortunately it's been quite some time ago. I would Google the subject to find the specifics, or if you view the source of any of those emails you may have in your own inbox, you can see how they set it up.
EDIT: I believe you actually set up the webpage and then copy the source code and paste it into the email. You then have to change any links to include the http:// part so that it knows to go out on the internet and not look locally on the computer. Again, I would Google for specifics or review and newsletters or ads you get in your own inbox.