The letter "M" is pronounced with a vowel sound at the beginning. Like "em."
You don't need a list of "exceptions," you just need to know how to pronounce a given word. If it begins with a vowel sound, use "an."
You are correct that "university" starts with a "yoo" sound. So it is "a university."
In contrast, "umbrella" starts with an "um" sound. So it's "an umbrella."
- For Teachers