Signature has problems - The certificate is not trusted and no parent was found

Whenever I receive a forwarded email from one particular colleague, I see the above message, and all the parts of the email are shown as attachments.  This is likely to be caused by an issue with his computer, because the certificate that is used to sign the email is actually one that he uses as a credential for some websites, so I don’t think it should be used for signing emails.
I guess the issue for me is that I wish to be able to read all emails that are sent to me (like I can on my phone).  In the specific case that I receive emails from this person, I’m not interested in whether the certificate is trusted or not.
How do I set up EM Client to show these emails in the normal way?

Hello Joe,

Please go to Menu > Tools > Settings > Mail > Privacy and enable the unsafe content from all users and see if it helps.
If not, could you send me an email with this .eml so I can check the settings by myself? Please send to:

Thank you.

I got also problem with emails from me, especielly when I RE: on mesages.
I generete signature (PGP) in emclient and I send it to EM keybook.
Coworkes (emclient) don’t see my attachemnts and messages text. I use 8.0.3385 version.