1. when the email arrives, it appears to come from 'Anonymous (Confluence)' .. in the email server settings from: is set to: ${fullname} (Confluence)
so $(fullname) is resolving to Anonymous, which is a bug, because the admin full name is set to 'System Admin' in the admin profile....
2. when the email arrives in the destination inbox, there is no visible link .. however if i hover over the space at the bottom of the email, there is a clickable link there (you just can't see it) .. and clicking it sends you to the signup web page...
UPDATE: #2 appears to be a bug in the email client .. as it showed up ok when I send an invite to Gmail ...