I’m with Ravedesigns on the benefits of phone calls and letters.
Sending an email is probably the most useless thing it is possible to do.
At the very minimum, try a carefully planned phone call.
For a better approach, phone and find out the name and job title of your relevant decision maker, but don’t talk to them yet (unless it’s unavoidable, eg. because they answered the phone). Send them a letter in the mail, briefly describing why you’re writing and what you can do for them. The persuasiveness of the letter is not critically important - it’s mainly sent to help with the next stage. It also marks you out as different - and perhaps more professional - than those who rely on just an email.
Leave it a couple of days and then phone the person. Typically you may have to get past a receptionist or secretary, in which case the inevitable ‘What is it concerning?’ question can often be circumvented by some variation of ‘It’s about a letter I sent last week’. If you get squashed by the gatekeeper it’s just too bad. You can’t win 'em all. Practice makes perfect. Your tone of voice and an air of polite confidence will make a great difference to your success rate.
Once through to the person you need to quickly introduce yourself and say something you feel comfortable with, such as ‘I’m following up on the letter I sent you last week.’ It doesn’t matter if they say they don’t remember it or they haven’t read it (or even confirm they did read it), because whatever they say you will quickly summarise its contents to set the scene and then attempt to engage them in discussion. The rest is up to you. Now you need to ‘sell’ the next stage (and ONLY the next stage), which is perhaps providing an estimate, or setting a face to face meeting, or whatever. One step at a time. Each step ‘sells’ the next step. And by ‘sell’, I don’t mean some silver-tongued, pre-packaged, cheesy ‘me, me, me’ spiel, but a low key, consultative discussion during which you mostly ask questions.
Proper businesses are quite happy receiving professional sales calls about relevant opportunities from professional sounding sales people - this is how most trade is conducted in the real world, after all.
Businesses don’t sell to businesses, people sell to people. Human contact makes a lot of difference. 
Paul