Google Workspace sender stuck at SCL=5 to all Microsoft-hosted recipients

Hi, passing SPF/DKIM/DMARC is necessary, but it does not automatically give a new domain good reputation with Microsoft recipients.

For a new Google Workspace domain, I would warm up sending slowly, keep volume consistent, avoid link-heavy test messages, avoid URL shorteners, and make sure DKIM and DMARC alignment are clean. If Microsoft 365 tenant recipients are available to you, have their admins submit the messages as false positives through Defender/Exchange reporting, because that gives Microsoft a much better signal than just users moving mail out of Junk.

For Outlook.com recipients, the Postmaster/support request is the right route, but there may not be a fast override if the domain is simply cold. Also check whether the domain, not only the sending IP, appears in any reputation or block systems. Unfortunately, for brand-new domains, a gradual warm-up is often part of the fix.