What can result in mailing to a large database of email addresses?

Question

Email

The situation is this:
There is a server with fully configured MX and SPF records, DKIM signature.
There is a database of Email addresses (it turned out after combining two projects).
What can result in sending messages with advertising content to a large database of Email addresses?
(the content refers strictly to the subject of the project)

Answer 1

If customers did not consent to the mailing, the company may receive a fine. The domain will most likely end up in spam. You can read more about this here: https://www.unisender.com/en/blog/sovety/ne-spam-k...

Answer 2

From the legal side
From a technical point of view, it is fraught with getting into spam lists.