You seek to understand how Email Security.cloud determines whether a given message is spam or is a newsletter.
Please see the following excerpt from the online help for Email Delivery.cloud:
Spam is defined as any unsolicited commercial email from unknown sources. The sender obtains the email address without the recipient's approval. Examples include phishing emails, advance-fee fraud scams (419s), and emails touting pharmaceuticals.
Newsletters are commercial emails. To receive a newsletter you need to subscribe to a mailing list. You may opt in unwittingly as part of a software installation, download registration, or membership registration. Examples of Web sites that opt users into email newsletters include Facebook, LinkedIn, and updates from company Web sites.