how to stop Mail Attachment.html in email

Situation: Many emails that I receive have an attached file "Mail Attachment.html" and it is often blank, or it will have the persons signature in it. Occasionally it has an entire email in the file.

What in the world is going on, why would this be happening and how do I stop it?

Google hosts our company's email with our own domain, and GoDaddy points the MX records.

I don't recall having this happen until recently and I'm a long time Mac Mail[.app] user.

No idea if it's a cause of a recent update or something that happened with employers system or what.

 

btw - this happens with plain text signatures, not with logos and links.