SocialX wrote: Why does invalid.com show up in the approval list when someone signs up through Twitter?

Because twitter does not share email addresses.

Twitter doesn't give you an email address. Yet Joomla absolutely requires one to register. So the only solution is to force an invalid address. When they attempt to edit their profile they will not be allowed to save unless they change it to a valid address however. You can also set the registration redirect to point to profile edit if you like.

Doesn't matter anymore, latest release won't allow invalid email addresses anymore. They'll be asked to supply a valid email address upon login and if invalid is supplied at registration time it'll suppress the emails (nothing will send).

Regarding the domain, it should've never been registered. Someone registered it before it could be reserved like example.com. Using invalid.com or test.com for example is just asking for spam and a poor way to promote a business. It's sad to see such a high potential domain wasted to be truthful.