In the footers directory you find some files that are examples of how the
footers are handled by t-prot. Those are the footers for most of the debian
mailing lists. Notice that the debian- footer is a stripped one which matches
most of the lists. t-prot checks for start of line matches.

 You can directly use them if you add the options
-l -L /usr/share/doc/t-prot/examples/footers
to your call to t-prot.