I am not a pessimist, but emailing Senators rarely works. The Senator to people ratio is just too large. You are better off starting a change.org petition or some other media type campaign where you can get some viral growth and visibility.
I've heard ex-staffers say that emails are worthless but calls—in volume, as you say—have an impact.
Too bad there isn't a standardized way for citizens to voice concern, such as an online poll conduced in a neutral manner. The whole call your representative this g always struck me as a waste of everyone's time, especially considering they just talley them.
My good friend from high school worked for Senator Dodd as an intern in the late 90s. This was exactly as he described it.