I created an app for a popular shopping cart. It is now listed in their app store and it gaining some traction, but not as much as I'd like. The idea for the app came from users asking for it so I know that it is much needed. I think the challenge is that people just don't know about it; I need to educate them. So, I've realized that I can buy a list of online stores who use this shopping cart. Then I can find their contact information.
My question is, how do you recommend that I get in touch with them? For example, I can send out a mass email, but of course that is spam and everyone hates that. Any ideas?
Depending on who is trying to selling you the list, you may find that there is already a legitimate email newsletter going out to the list.
Instead of purchasing the list, you could perhaps spend the money instead on purchasing an advert in that existing newsletter. This would be most effective if you were able to offer a valuable and appealing white paper or such like that would require people to sign up for and consider opting in to a newsletter of your own.
It is incredibly tempting to just mail the list directly, but there is no getting away from the fact that it is then spam.
On a broader point, the people you are trying to reach are likely to be technical and spend a fair amount of time online, possibly in quite predictable places. Therefore classic inbound marketing / content marketing strategies are likely to work well and reward the time investment involved.
Just make sure your emails are personalized and address the real need of these websites. Maybe start by sending the emails manually, see how responses look like, fine tune you pitch.
If you're interested in getting the list of the websites that use this particular shopping cart solution - let me know, I know one source that provides a small part of this information for free.