I recently received a digital signed email from a friend and the certificate is issued by COMODO RSA Client Authentication and Secure Email. My problem is the thunderbird detect it as a "Not Valid Signature"

Here's the pic:

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I double checked the CA Authorities on thunderbird and it is already trusted, now I can't reply an encrypted and digitally signed email because of this problem. How do I fix it?

  • 1
    Can you check that the CA Authorities certificate in you store and the CA presented here have the same fingerprint ? – Whysmerhill Feb 15 '19 at 14:17
  • Was the certificate still valid when it was used to sign? – Lithilion Mar 11 '19 at 13:12

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