One of the biggest misunderstanding’s I see around Microsoft/Office 365 is managing anti spam settings. These are done in Exchange Online. Thinks like Office 365 ATP actually perform additional functionality (such as safe list and attachments). Thus, if you want to limit the spam that users receive it is important to ensure you have your anti spam policies correctly configured.
This video will show you how and where to configure both inbound and outbound spam policies as well as some best practice recommendations for both. You’ll find the direct link for the video here:
CIAOPS 