> how about using List-Post? Might be better suited.
How about this?  (Given a format of
 "List-Post: <mailto:docs at xxxxxxxxxxxxxxxxxxxxxxx>")
:0
* ^List-Post: <mailto:.\/[^@]+
{
 LISTNAME=${MATCH}
 :0:
 * LISTNAME??^\/[^-]+
 DragonFly-${MATCH}
}