To fix this, work with your DNS hosting provider (your domain registrar, Web hosting provider, or ISP) to set up a correct ...

To fix this, work with your DNS hosting provider (your domain registrar, Web hosting provider, or ISP) to set up a correct PTR record for your domain.

If you're using Office 365 to manage your DNS records note that PTR record creation and management isn't supported by the Office 365 interface, in which case you'll have to change your DNS management to a DNS host outside Office 365. Refer to this article for instructions on how to do this:Change how DNS records are managed with Office 365.

Setting up PTR records is not supported by Office 365. Office 365 support will not be able to help you fix these kinds of externally reported errors.