Business to business emails are not considered spam under the CAN SPAM ACT, but the receiver may feel differently. I'm not saying to do it or not do it, but consider the end user. Perhaps you should start out slow and see what the response is like. If you get a lot of complaints, cease. If the recipients are responsive and happy to hear from you, proceed.

I would say it is ethical to email a company if you have something good to offer them or an interesting partnership. However, I highly doubt that you're offering a company anything worthwhile if you're sending out 200-300 emails a day. That's called spam, not marketing.