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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

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?

Daniele Santi
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shiroyashaa
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1 Answers1

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It appears that COMODO RSA Client Authentication and Secure Email CA is not installed in thunderbird.

You may need to download the certificate and install in the thunderbird. I suspect, the talk is about the certificate provided here: https://support.comodo.com/index.php?/Knowledgebase/Article/View/1148/106/comodosha256clientauthenticationandsecureemailca

In Thumberbird, go to Options -> Advanced -> View Certificates. In the certificate store view, click on Import and select the CA certificate. When prompted select the Trust this CA to identify email users option. After this operation, email signature should be successfully validated.

Crypt32
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  • The certificate is already trusted, I don't why it doesn't work. I installed a different client and it works perfectly fine. – shiroyashaa Feb 15 '19 at 23:47