Hi,
Having owned a commercial cleaning business and helped many commercial cleaning businesses with their marketing, I recommend against your approach.
What sort of businesses do you tend to work with? There is likely to be a floor space, business type, location, and so on, that you prefer? Find other businesses like those and target them. This is something I can absolutely help with.
I can also help with getting the message just right to target that 'segment' of business.
A small, targetted list is better than a large list.
For example, my cleaning business was dedicated to providing the most environmentally responsible service is our city - the chemicals I used, the methods, my transportation (cargo bikes), and every other aspect of the business. As such, our primary customer was environmentally responsible businesses. Our secondary customer was businesses that had some form of social responsibility and/or sustainability policy. We only targeted these businesses and then, only of a certain size.
Looking forward to hearing back.