SPF

   The Sender Policy Framework (SPF) is an email-authentication technique which is used to prevent spammers from sending messages on behalf of your domain. With SPF an organisation can publish authorized mail servers.

Microsoft Office 365

   Microsoft Office 365 is a Software as a Service (SaaS) solution that includes Microsoft Office and other services, such as email and collaboration, from Microsoft’s cloud server. Microsoft Office 365 provides desktop functionalities and is available by subscription.

No Cache Content

   Forces caches to submit the request to the origin server for validation before releasing a cached copy.

NO Store HTTP Cache-Control

   The cache should not store anything about the client request or server response.

HSTS - Browser HTTPS Only

   The HTTP Strict-Transport-Security response header (often abbreviated as HSTS) lets a web site tell browsers that it should only be accessed using HTTPS, instead of using HTTP for 63072000 seconds