Tenant has exceeded threshold" NDR when mail is sent from your organization - O365andAzure
SharePoint Online: "Access denied. You do not have permission to perform this action or access this resource" Error on Uploading File, Creating Folder in Style Library - SharePoint Diary
Email non-delivery reports in Office 365 – Microsoft Systems, Cloud and azure professionals
Remote Server returned '550 5.7.705 Access denied, tenant has - Microsoft Community
550 5.7.705 Access denied, tenant has exceeded threshold - Microsoft Community