sendmail_path :: String,
from_address :: Maybe String,
to_address :: Maybe String,
sendmail_path :: String,
from_address :: Maybe String,
to_address :: Maybe String,
(merge' (from_address cfg) (OC.from_address opt_cfg))
(merge' (to_address cfg) (OC.to_address opt_cfg))
(merge (verbose cfg) (OC.verbose opt_cfg))
(merge' (from_address cfg) (OC.from_address opt_cfg))
(merge' (to_address cfg) (OC.to_address opt_cfg))
(merge (verbose cfg) (OC.verbose opt_cfg))