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Verify the digital signature on a signed email message

When someone checks your identification to make sure that you are who you say that you are, it’s important that they match the identification photo with your face. Similarly, when you receive a message in Microsoft Outlook that contains a digital signature, it’s important to verify that the signer is who you think that the person is.

  1. Open the digitally signed message.

  2. Look at the Signed By status line to check the email address of the person who signed the message. It isn’t enough to check the email address in the From line — you want to verify who actually signed the message, not only who sent the message.

    Important:  If the email address in the From line doesn’t match the email address in the Signed By status line, the Signed by line is the one that you should use to determine who actually sent the message.

  3. To check whether the signature is valid, click Digital signature icon on the Signed By status line. Then, to see more information about the digital signature, click Details.


    • If a digital signature isn’t valid, there can be many causes. For example, the sender's certificate may have expired, it may have been revoked by the certificate authority (CA), or the server that verifies the certificate might be unavailable. Notify the message sender of the problem.

    • If a delegate sent the message on behalf of another person, then the delegate's name is listed as the sender.

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