As discovered in the spike task (T326923), the following needs to be changed:
$user = User::newFromName( $title->getRootText() ); if ( !$user || !$user->getId() ) { // Does not exist
MassMessage doesn't allow posting messages to anon talk pages. I believe it should also not allow posting to temp user talk pages.
Acceptance criteria
- Mass messages cannot be sent to the talk page of temp users


