Ask HN: Can I force Big Email Company to not mark my emails as spam?

We are running a business where people buy a product in a webshop and receive an email "Thank you for purchasing the product. Here is your licence key".

Now Big Email Provider are marking those emails as spam. Even though

- every single email we send is an important email that our users really want to read - our email is following all known to us good practices - our domain has never been used to send any unsolicited emails ever - they are simple plain-text emails without links - we usually send not more than 3-5 emails a day to Big Email Provider - we ask our customers to mark them as "Not Spam" and they claim they do so.

Big email providers refuse to not mark our emails as a spam. "We know it's not a spam, but we are still going to mark them as spam to our customers and we won't tell you why."

It's hard to calculate the exact damages but it does damage our reputation because frequently pepole don't check spam and send us angry emails or publicly complain that they haven't received an email for a week. (Our replies to these emails aren't sent to spam).

Is there any precedence where someone has succesfully managed to force Big Email Provider to not mark legit emails as spam or have there been any lawsuits anywhere around this topic?

Edit: we do have proper dns settings, send emails from big email provider ourselves and did our due diligence including discussing topic with external experts etc. For the purpose of the question please assume that we do everything by the book and the reasons for the issue are hidden even from the big company in their ai- based spam filters. We did get response from those providers that "your emails are fine, you do everything right, but our ai marks them as spam and we can't and won't do anything about it"