Unable to send emails in new Outlook for macOS and Windows

Products

• Cloud Secure Web Gateway - Cloud SWG

Issue/Introduction

You are using the 'new Outlook' feature in Outlook for macOS or Windows.

Sending/receiving emails doesn’t work.

Downloading/syncing the mailbox doesn’t work.

There are no issues if you revert to legacy Outlook mode or use web version of Outlook. 

Environment

Affected Outlook for macOS version: 16.89, 16.98

WSS Agent

Cause

CloudSWG reporting shows verdict invalid__request for https://outlook.office365.com:443/outlookservice/servicechannel.hxs

Only the new Outlook mode on macOS Outlook is affected by this issue.

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invalid_request DENIED "Business/Economy;Email" - 400 TCP_NC_MISS_RST POST application/httpsocket.wbxml https
outlook.office365.com 443 /outlookservice/servicechannel.hxs

Resolution

CPL code must be implemented in the customer tenant. To proceed with this implementation, please contact Support so that Engineering can add it to your policy.