Cloudflare DNS Cert Warning showing in Outlook?


Could anybody provide some advice on the following:

I have a client who is getting intermittent warning popups in Outlook about the following cert:

Can anyone why this is happening, client is using Exchange via Office 365, by way of Telstra. Name servers of the domain don’t point to Cloudflare name servers.

What are they connecting to that’s giving them the SSL certificate for Cloudflare’s DNS website? is issued for But it shouldn’t throw a warning. What’s the exact error message?

So to clarify what @sdayman asked, thats the question :slight_smile: I don’t know either, so I’m not sure how to go about troubleshooting it. I have never encountered it before.

@MarkMeyer the dialogue box prior to the other screenshot already shared is:

Seeing that one, and the other one together (they were sent days apart) makes it a lot clearer to me. But I still don’t understand why that Office 365 cert is ultimately issued by Cloudflare? Is this a local network ‘issue’ or something domain side?

Thank you both for taking the time to reply to my initial post.

Yes, but the URL is incomplete so there’s no screenshot. Look at your first post. :wink:

Cloudflare doesn’t issue certificates for Microsoft. I am not sure but it seems that there
is something messed locally. Do they use as DNS servers? but even then they shoud not get this warnung.

Not sure how that markup made its way into my post, i’ve edited the post. But its just the two screenshots, there is not a 3rd.

What I might do is try and replicate the issue on a different network/computer.

The unusual thing is that the certificate cannot be saved/installed either, but this may just be the end user’s computer literacy at play.

I’ve also just noticed Cloudflare has released a consumer DNS service. Does Cloudflare have any deals with antivirus or VPN software that would change the user/network’s DNS as a security/performance feature?

I will check to see what DNS the computers are using.

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