How to forward emails including long headers?

Until recently it was possible to reveal all the headers on scam emails and forward the complete scam email, including all the headers, to Scamwatch.

With the latest version of Mail I can’t find a way to forward the long headers. A few times I’ve copied then pasted the long headers from the offending email and sent them to Scamwatch but it’s not the simple process it used to be, that is, showing them all and forwarding the complete email.

I’ve tried sending as an attachment but that didn’t work either.

Is there a better way to forward the long headers, please?