;; uses mu4e-fetch-field which is rel. slow, so only appropriate
;; for mu4e-view-fields, and _not_ mu4e-headers-fields
:function (lambda (msg)
;; uses mu4e-fetch-field which is rel. slow, so only appropriate
;; for mu4e-view-fields, and _not_ mu4e-headers-fields
:function (lambda (msg)