Personally I don't do it. It's fine if you speak with a provider and you are following up via email but as an initial contact I say NO. First impression's are too strong to risk with email marketing. Use the internet more efficiently by having a website to refer potential clients to in your direct mail. You want to be careful though and make sure your website is professional, not to much bling, not too bright because you could actually chase a provider away. I had a small company send me a really nice letter and biz card offering computer repairs and home network setup, etc. It just so happened I was in need of one so I went on over to their website and was horrified... scrolling text, blinking art, bold and gross colors and well I didn't get beyond the first page and he didn't get a call from me.
JMO If you are going to use the internet, do so WISELY!