Outlook prompting for certificate

Niranjan T Pattana Shetty 266 Reputation points
2020-08-03T09:42:50.353+00:00

Hi all,
Thanks in advance, all of our mailboxes are stored in Office365 and when we run our Outlook we got a certificate alert, on clicking "No" the connectivity status showed disconnected. But, on clicking "Yes" the connection got established.

So, just wanted to know how do we validate whether that was a genuine certificate or a spam?

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2 answers

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  1. Vasil Michev 61,991 Reputation points Microsoft MVP
    2020-08-03T09:56:56.783+00:00

    Click the button and check the properties of the certificate? It's usually either because the connection is hitting an on-premises Exchange box, or being intercepted by an SSL offloader or such.

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  2. KyleXu-MSFT 25,616 Reputation points
    2020-08-04T02:43:47.913+00:00

    Do you run a hybrid organization with Exchange online and Exchange on-premises? Or only using Exchange online?

    Could you provide detailed screenshot about this certificate prompting? It could help us to narrow down it.

    As far as I know, Exchange online certificate is provided by Microsoft, there shouldn't exist any issue with certificate.

    >"validate whether that was a genuine certificate or a spam"

    As michev said, you could check the Issuer from the Details label in certificate properties(The picture below comes from the certificate for Q&A rather than Office 365)
    15307-snipaste-2020-08-04-10-41-26.png

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