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Outlook hangs evaluating content when Purview over sharing popup policy is applied

Cng 15 Reputation points
2025-10-02T18:45:27.5466667+00:00

When a Purview oversharing popup policy is applied to warn users if they are about to send their e-mail to external recipients, sending of the e-mail intermittently hangs with an "evaluating content" message if the dlpwaitonsendtimeout registry setting is applied (without this registry setting, Outlook does not enforce the policy). This problem is extremely intermittent and meaningful/efficient testing has only been possible using macros to bulk send e-mail. Sometimes the problem occurs when the first e-mail is sent and other times 1000 e-mails can be sent without reproducing the problem. Network captures show that every successful e-mail generates both a websocket upgrade and a websocket close with augloop.office.com. When e-mail sending fails only a websocket upgrade and no websocket close can be seen. The problem was originally reported on internal clients sitting on a company network, on a VPN and behind company proxies, but has since repeatedly been reproduced from Microsoft Azure Virtual Desktop, which is not on the company network or VPN and not behind the company proxies. Has anyone had any experience with this or any thoughts about it?

Microsoft Security | Microsoft Purview

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  1. Prathista Ilango 670 Reputation points Microsoft Employee
    2025-10-07T10:32:44.8233333+00:00

    Hello Cng,

    Since the issue is intermittent, it's tough to reproduce. Try fiddler trace and Outlook ETL logging to check if you can find more information on why the websocket close is not seen.

    Also, make sure to try this with simple policy rules not with many conditions and rule checks to avoid complexity delays.

    Check the dlpwaitonsendtimeout regkey seconds value and set it to a longer duration if evaluation is taking time than the configured seconds (Ideally, in this case you should get a Send Anyway button).

    If the above doesn't help, try to gather the traces and reach out to support: https://support.microsoft.com/en-us/contactus#!
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