How do I invite people to my site?

Like you do on Facebook you can invite people. I would like to invite people directly from my site. How do I do this?

At the moment I do this using Outlook but want to do it from my site.

Regs

Simon

Dolphin 7 I am using

As I know Dolphin7 hasn't got integrated mass mailer, that can send emails to addresses not registered on the site.

Hmmm.......  That can't be right?  What is the purpose of the feature as well as the letter that goes out which I have edited to attract people to my site.  If what you say is correct and I am certain it is not that would be a HUGE step backwards.......The issue is the email address going out must match the domain it is sent from........@yourdomain.com         Gorpus can you advise about that answer??