Here's something I've been trying to understand... take a standard jazz progresion in Aminor. It would look like this: Bm7(b5)-E7(b9)-Am7

My question is this: Why would the V chord (E) be major? A minor contains Em, not Emajor- unless of course you're talking A harmonic minor.
I'm sure this is brain candy to some of you but I've been struggling to understand why this progression would have an E7 and not an Em9!