The default configuration for Office 365’s Exchange server is to automatically respond to requests for mail delivery reports. If like me you don’t want to divulge this information then here is what you need to do.
Follow these steps to block all forms of email delivery and read receipts …
Exchange Admin Centre > mail flow > remote domains > Default Untick 'Allow delivery reports' and 'Allow non-delivery reports' Save
Exchange Admin Centre > mail flow > rules > + Create a new rule > More options... Apply this rule if... The Sender is located... Outside the organization Do the following... Modify the message properties... Remove a message header (paste a header as above) Save
Outlook > Settings > View all Outlook settings > Email Message handling > Read receipts > Never send a response Save