if your email signature/name gives away too much information about you, you could be getting intentionally ignored. I know it's not legal in many places, but it happens.
I had a lot better luck getting initial replies when I stopped showing my name on my emails. still got shot down several times by people only wanting to rent to women, because men "tended to cause more damage."
and what Sluggo said also holds some truth. if they offer an option to look @ the property, take it, as that indicates that you're more serious.