I think it fair to say that laws and regulations typically do not indicate what you can do, only what you cannot do.
There is a basic assumption that if the law doesn’t expressly prohibit an act then it is permissible under law. Having said that, you do need to be careful with any law that is written ambiguously as it can be and sometimes is, interpreted at the whims of regulators.
To truly understand the law you need to have a good deal of knowledge about the contested interpretations that are codified by court cases. In other words, seek the advice of a lawyer that specializes in the pertinent law, or take your chances. Seeking legal advice on a forum might not be the wisest choice.
I’m not an attorney, but I do believe the law relates to privacy concerns and is not meant to apply to business the same way as to consumers. However, there are certain aspects that apply to all parties. In addition, the various ISPs all have their own internal policies that are not subject to the CAN-SPAM act that regulates usage on their own platform that typically is far more restrictive than the law, so you need to consider those policies in your practice.
To be sure, any kind of unsolicited bulk mailing is going to be hit with many issues, both legal as well as industry-standard policies and practices. Just because it is not illegal does not mean messages will be allowed to be sent over networks owned by private service provider companies.
I recommend that you learn and adapt to all industry standards and practices as they will likely be well within the confines of the law, and you need to meet those standards anyway to get your messages reliably delivered.