-transport. The check is necessary at delivery time in order to handle homonymic
-addresses correctly in cases where the pattern of redirection changes between
-delivery attempts (so the unique fields change). Non-homonymic previous
-delivery is detected earlier, at routing time (which saves unnecessary
-routing).
+transport. If it has been delivered, mark it done. The check is necessary at
+delivery time in order to handle homonymic addresses correctly in cases where
+the pattern of redirection changes between delivery attempts (so the unique
+fields change). Non-homonymic previous delivery is detected earlier, at routing
+time (which saves unnecessary routing).
+
+Arguments:
+ addr the address item
+ testing TRUE if testing wanted only, without side effects