Board Thread:Support Requests - Getting Technical/@comment-4061770-20140704224432/@comment-5558012-20140705002928

You seem to be referring to MediaWiki:Welcome-message-wall-anon and MediaWiki:Welcome-message-wall-user. These are sent automatically to those new users of wikis with message wall enabled. Message wall greetings are the messages seen at the top of individual message walls. Here's an example.