I've validated a solution, have a few committed customers, and want to move forward with development and subsequent marketing of my app. In validating the solution, I simply went onto the yellow pages (YP.com) and got email addresses of local businesses from which I sent an email simply asking if they had the problem, not pitching a solution. This resulted in a very good reply-rate, which I was then able to begin a direct conversation and turn it into commitments.
Now that I want to broaden my scope of marketing, I'm considering the same approach, but don't want to wind up spamming people. I could begin email folks using the same approach, but this seems a bit time consuming especially if we are talking 1000s (but may be necessary) as I'd much rather write a solid email that gets right to the point.
Adwords is of little value as my customers aren't actively seeking a solution online, but once they are made aware of mine, then its been well received.
Any advice on what to do next/best way to approach this is greatly appreciated!
When emailing people who haven't chosen to be contacted, is like phoning out of the blue or knocking on the door it is an interruption to their day. So therefore you should always consider how to minimise the interruption, find a way to engage them and give them a hook to the engagement without requiring an immediate commitment. It sounds like your first approach ticked these boxes, I often find the best way to get sales is to start with a question it builds the right mindset it get's people thinking, it also requires no commitment, they can choose to engage with my question or they can ignore it and let it niggle at them in the back of their minds.
In terms of scaling your existing technique, if you haven't already invested in a CRM solution such as CapsuleCRM or SalesForce then now would be a very good time, replying to emails can be time consuming, but with a few canned responses and a few seconds to personalise the email to their original answer you can dramatically cut the time taken. With a cRM you will be able to see interactions, and generate task lists such as when is the time to reply or to follow up. Most CRM provide you to add your own notes this helps you to identify points about a given customer and help build the relationship up. Secondly I would invest in some sort of mail analytics you could use full email marketing systems like MailChimp but they do tend to frown on unsolicited emails and really are more aimed at bulk broadcasts. Instead you could look at solutions such as ToutApp which provide analytics from within outlook or gmail.
One thing that we realised was as we lost the human element we also started losing sales, now depending on your price point, the amount of human effort may not be justified its all about finding the balance, but I would also suggest that your first contact should be a question, not an answer.