"no visible content" SMIME.p7s

Hi

We have our Gmail account connected to Zammad. For this one particular customer their emails come into Zammad with “no visible content” and a smime.p7s file attached. But the content of the emails can be viewed within Gmail.

I understand this is a form of encryption on their end.

Is there some type of filter setting within Zammad to toggle so we can view the contents?