When I run fidentity on an existing file it is reported as html. These files have no extension so I am a bit perplexed as to how to design a custom signature. They are named Inbox, Sent, Trash, and whatever folder name the user may create. As best I can tell they are ascii files starting with the text "From -". A photorec.sig file containing
returns far more files than I can analyze.custom 0 "From -"
Also, what would be the signature for files identified as html by fidentify?