WINONA, Minn. — After deciding an email threat of campus violence wasn’t credible, Saint Mary’s University ended an eight-hour lockdown. Classes resumed at noon. The threat was in a lengthy and mostly unintelligible rant. A possible clue to the source was a claim to being denied admission. A scan of Saint Mary’s admission records would narrow the list of suspects. The fact about admissions, however, is that Saint Mary’s refuses hardly anyone. All that’s required these days is a high school diploma and grades averaging a C. Admissions exams like SATs and ACTs are only optional. As requirements, the exams were scrapped years ago.