I use email along with call, write, fax its all a part of my target marketing. I used to have a service when my nephew worked for me and he would take care of it. Now I just have different lists that I send to
Key I think is not to over use email in a total campaign, don't want to junk up peoples emails every week and aggravate them so they never open your stuff
Emails definitely work in my niche, many times I get responses that say..... perfect timing, glad you sent me an email. Its also good for following up with potential customers on bids given.