email cert vs. non common mail clients

I’m using cert with Outlook 2003. Sending to users with common email clients is OK. Means thay can see cert etc.

But people with kmail client ( https://kontact.kde.org/components/kmail/ ) experiencing problems with my cert.
They are getting error: cert is unverifiable.
details: CN=Alexandr Sivilirov,EMAIL=my@emailaddress.com,OU=(c)2003 Comodo Limited,OU=Terms and Conditions of use: Endpoint Detection and Response, Free - What is EDR Security? Trust Network - PERSONA NOT VALIDATED

Anybody know how to get it to VALID?

Hi,

The only way to get a validated email certificate is to purchase one.

You could contact our sales team, details can be found at http://www.instantssl.com
for details of what is available.

However, the issue you are seeing sounds more like KMail is using a root certificate store that does not have the AddTrust External CA Root in it.
‘unverifiable’ suggests to me that it cannot find a chain to a trusted root.

So, you might want to contact the providers of KMail on this one.
We sign purchased email certificates from the same root, so checking this would be the first step you would need to verify.

Garry