Newsletters are Tiki-managed email lists. Users may add their email addresses to newsletters through the Tiki and admin can then use newsletters them to notify subscribers about site features, maintenance and upcoming events.
Register at tiki.org and you'll be able to use the account at any *.tiki.org site, thanks to the InterTiki feature. A valid email address is required to receive site notifications and occasional newsletters. You can opt out of these items at any time.