How to forward as attachment with KMail filter

Hello,

I'm having trouble figuring out how to automatically forward mails as 
attachments. I see that in the filters there is the option to Forward to, but 
this does it inline.

Looking at making a custom forwarding template there doesn't seem to be any 
attachment-related options. All commands relate to modifying the headers or 
message body.

When reporting spam for example, what's the best way to automate this?

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