One option is mayhem.
A six letter word for a bird of prey starting with the letter R is "raptor."
canalscanarycancelcancercandidcandlecandorcaninecaningcankercannedcannoncanoescanopycantercanvascanyon
A six letter word for undeliverable mail is nixies.
listen
Hawaii
Cycles
Auntie?
jamoke
origin.
Gannet
apogee
bighug