There is a new pull request by therealfun against master on the mblaze repository

https://github.com/therealfun/mblaze magrep-invert
https://github.com/leahneukirchen/mblaze/pull/201

Match messages without a specific header when "mgrep -v header:match" is used
My main usage is to pipe messages through `mlist ... |magrep -v to:addr |magrep -v cc:addr`.

I'm not sure the patch is complete, but still...

A patch file from https://github.com/leahneukirchen/mblaze/pull/201.patch is attached