security certificate revoked - outlook.office365.com

Hi there,

As you have stated that you have not connected to any domain can you please check if you have updated with all patches and try disabling your firewall and see if you are getting this message?

There is some weird behavior in Outlook in connection with O365. Apparently, Outlook checks the validity of all your validated domains in your tenant but shows as error "outlook.office365.com cert revoked".

Have you verified that you can contact the CRL from within your network and that the certificate thumbprint of the cert you are getting the error with isn't in that list?

Hope this resolves your Query!

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Hi @John Rovel Kalaw ,

Welcome to our forum!

Based on my experience there are some possible causes you can try to check on your side:

1.Proxies or firewalls.

2.MTU limits. Some reports also indicated it only happened on specific networks like WiFi or network provided by specific ISPs. It ended up with the root cause is MTU limits in these networks.

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Just ran into this myself. The subject of the certificate isn't the issue, as not only would the error be different, but the outlook.office365.com domain is covered by the SAN (Subject Alternate Name) field.

The certificate I ran into the issue on has the fingerprint: f7da87b0b58b2a2eec386ec7a60ab14d5a60a499

I have attached a copy of the certificate 254502-revoked-ms-certcerb64.txt

We are having the same issue on a few systems in our environment as well.

The security certificate revoked error pop-up occurs at random times for on-premises users and remote VPN users (VPN is configured to split-tunnel mode).

As per Microsoft support, we updated the Outlook client to version 2202 and created new outlook profiles, but the pop-up still occurs. Time is also synced.

Yesterday the error started popping up on my machine several times as well.

So far, we can see this error only for SSL certificate from Digicert Cloud Services CA-1 with serial number: 0f12dc8955821d6d936bcf34e50f60c5 that is currently used by outlook.office365.com

We're hearing reports of this for on-premise users of M365 starting this morning. we use Fortinet Fortigate firewalls, wondering if this is a certificate inspection issue with an outdated or incorrect CRL list.

Chris