It often pays to do a search first with relevant keywords. The automatic search using the words in the title-box can get confused if the important keywords appear later.
That said, I just tried typing the title of this thread into the new-thread title box, and the article I linked showed up as suggestion #4 of 5. Maybe all the recent searching for keywords "old mail" has moved it up in the results rank, and it wasn't there when you started the thread.
I also did a test typing keywords old mail into the new-thread title box, and that article appeared at 4 of 5. Adding "settings" moved it up to #3 of 5.