I’ve had a similar experience when signing up for Office365 and started getting promotional emails to CoPilot. These (2) emails were without an unsubscribe option.

I contacted MS support and after some back n forth they claimed it was a transactional email that doesn’t require consent or opt out.

Clearly promotional and not necessary but they won’t listen.

I’m in the process of filing GDPR + ePrivacy complaints, but it’s a tedious process, unlikely to do anything.