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

There is no sender-side switch that instantly resets Microsoft reputation.

SCL 5 by itself is not enough to identify the root cause in cloud filtering. Check the X-Forefront-Antispam-Report header and review the CAT, SFV, and BCL values.

If you see CAT:SPM or SFV:SPM, the administrator for each affected Microsoft 365 recipient should submit the original message as a false positive through the Microsoft Defender Submissions page. Microsoft may create a temporary allow entry while the submission is reviewed.

For Outlook.com recipients, continue with the Postmaster Sender Support case and follow the automated response instructions exactly, otherwise the case may not progress.

Keep sending volume consistent, avoid unsolicited test traffic or lists that may generate complaints, and allow time for sender reputation to improve. SPF, DKIM, and DMARC confirm sender identity, but they do not override Microsoft reputation filtering.