Why is mail not being delivered through the Office 365 API from the web app?

Question

API

The web application sends emails via the office 365 api, they are returned undelivered with the wording 'Remote Server returned '550 5.7.501 Access denied, spam abuse detected. For more information please go to go.microsoft.com/fwlink/?LinkId=526653 '
This only happens in the combat version. From my local version on Openserver everything works fine. Tell me where to dig, maybe someone came across