This feature was removed in Tiki21. Use Share instead.
Starting in Tiki5, it's possible to share access rights to a specific URL via Token Access.
This feature allows you to add a link "Email this page" in all the pages at the top of the screen.
If you click on it you will see
When you click a message to each of the indicated mails will be sent with your comment, the link and your name.
the feature is activated in the features admin panel
You need a perm tiki_p_tell_a_friend in the tiki section
Related: PluginSharethis