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Outlook Win10 S/Mime invalid certificate RRS feed

  • Question

  • Hello,

    I try to configure Outlook for s/mime encryption for myself and 3 other employees.

    Although the same steps were taken during setup, the encryption only works for me and one other employee, the other two get error messages.


    To check if the setup was successful, we first try to send a signed email. Here we all got an error message that means "Outlook can't sign or encrypt the message because the certificate is invalid".

    I was able to solve the problem, but only for me and another employee by changing the encryption algorithm in the Trust Center settings from AES 256 to 3DES.

    After that both of us were able to sign, encrypt and decrypt messages. Even after I switched back from 3DES to AES256 everything works.

    Unfortunately this approach did not work for the other two employees. Now i don't know exactly what it could be, has anyone ever had the same or similar problem and can possibly help me?

    • We are all using the same Windows, Office 365 ProPlus and the Outlook desktop app version 1908 build 11929.20838
    • Everyone has his own personal certificate.
    • The only difference I noticed so far is, that for the two where it doesn't work, the "publish to GAL" button in the Trust Center settings is missing.



    I am grateful for any advice.

    Best regards.

    Wednesday, July 8, 2020 6:12 PM

All replies

  • Hi ,

    >> I try to configure Outlook for s/mime encryption for myself and 3 other employees.

    I did some research and found some information of steps to configure s/mime encryption, please check the steps in this article and make sure you have configured it properly: Installing an S/MIME Certificate and Sending Secure Email with Outlook. (Note: Since the web site is not hosted by Microsoft, the link may change without notice. Microsoft does not guarantee the accuracy of this information.)

    >> Unfortunately this approach did not work for the other two employees. 

    To confirm if this issue is related to their Outlook client or their certificate, it is suggested to add your email account and your certificate to their Outlook client and see if the issue has any difference.

    Besides, as I know, corrupted Outlook profile may also cause issues like this. Please try to create and use a new Outlook profile via Control Panel > Mail > Show profile, only add one email account in this profile to avoid email match issues and see if it works.

    Hope this can be helpful.

    Regards,

    Jeff Yang


    Please remember to mark the replies as answers if they helped. If you have feedback for TechNet Subscriber Support, contact tnsf@microsoft.com.

    Thursday, July 9, 2020 6:17 AM
  • Hi ,

    Just checking in to see if above information was helpful. If you have any further updates on this issue, please feel free to post back.

    Regards,

    Jeff Yang


    Please remember to mark the replies as answers if they helped. If you have feedback for TechNet Subscriber Support, contact tnsf@microsoft.com.

    Sunday, July 12, 2020 7:35 AM