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Hi
The pictures below started popping up on our PCs. and the PC was using not part of any domain. I tried to follow the link below but the IE was inaccessible. https://answers.microsoft.com/en-us/outlook_com/forum/all/outlookoffice365com-security-certificate-has-been/743bdb2b-06ce-4206-923e-bdb7041528bd
Using classic Outlook for Windows in business environments
I am not a computer person and also have this problem. I clicked into the Security Alert message's "View Certificate" button and saw that the certificate is issued to "outlook.com" while the security message said the internet address "outlook.office365.com" has security concern. That to me essentially is a Microsoft mess up by using Peter's credential to do business as Paul.
I think that I started to have this pop up issue around when the new certificate became effective, that was 7/25/2022.
As to some PCs/Macs don't have the issue maybe because they already have the correct security certificate installed on their computers. There is no setting in my hotmail setup for me to change in Outlook, so so far I am dealing with it by clicking ok on the box everyday.
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Same issue with the certificate revoked. Cert in the Outlook desktop matches the cert in OWA. A ticket is open with Microsoft, but nothing yet
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Are you a Canada East Coast Tenant?
Just trying to see if there is a relation there. To further relay for my case with MS
Your question got me thinking. I am checking to see if the users that have communicated the certificate issue have mailboxes on the same server in the cloud.
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We are also seeing this in Ontario (Canada East datacenter)
We are on IPv4, and have seen it on WFH users on IPv4 only as well, so it is not isolated to IPv6 users.
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I got this popup this morning and also last week. It is random from what I can see. The cert has been revoked. What this means is that the software, in this case outlook has gone to the certificate issuer, to determine it's status. The certificate issuer for my current connection is DigiCert Cloud Services CA-1. This is random and Microsoft likely has a lot of servers that have a cert for outlook.office365.com, Likely one or more servers have not been updated with the correct cert. When your client resolves the name, the DNS system returns an ip address. It likely will not always be the same one. One must determine which server or servers have not been updated. Currently my outlook client is connected to more than one server and my browser is connected to a different one than outlook. This is just one of many and may or may not be the server with an issue. 2603:1036:30a:1425:0:0:0:2 This is an ipv6 address in case inquiring minds don't understand. To get to the cause of this one must find the specific ip address of the server that is sending the revoked certificate in response to a connection request.
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Located in Canadian east coast as well and using Windows 11 and outlook 365 version 2209 with the same issue. When I open the certificate and check the root and intermediate, they show up as ok.
Serial Number for the cert is : 0f12dc8955821d6d936bcf34e50f60c5
EDIT:
I tried removing modern auth and reactivated it. Will give let you know if the issue re-occurs.
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Wondering what folks are using for Firewalls/AV? Perhaps there is a corolation?
We usually have a setup of Watchguard Firewalls and SentinelOne or Crowdstrike.
I seem to have the issue at various locations, Usually we have a watchguard firewall and then one of those two EDRs.
