OpenInviter is a mass-mailing tool for social media which allows visitors of your site to invite their friends to your site using their regular email or social network accounts. This way they can invite their entire contact list in just a few clicks.
It is as simple as this: enter your email address and password, pick an email provider or social network, fill the message text and choose the contacts you want to send the message to, hit "Invite" and emails are sent.
Download the plugin and unpack it to your Cotonti 'plugins' folder.
Visit OpenInviter site and register an account there.
Edit 'plugins/openinviter/OpenInviter/config.php'. Put there your username and private key you obtained from OpenInviter site. Make sure "stats" is FALSE, otherwise the plugin may not work on some hosts.
Optional: rename 'plugins/openinviter/OpenInviter/postinstall_bk.php' to 'plugins/openinviter/OpenInviter/postinstall.php', run it from your browser and then remove it if everything is ok.
The link to the plugin is http://example.com/index.php?e=openinviter or http://example.com/openinviter (with handy urls).