Astate's civil procedure rules allow for "nail and mail" service (posting the summons at the defendant's dwelling and thereafter mailing him a copy by certified mail) when "regular" service (service by physical delivery or by leaving a copy of the complaint with someone of suitable age and discretion at the defendant's usual place of abode) cannot be accomplished with due diligence. a plaintiff brought suit against a defendant in the federal district court for that state. after the plaintiff's special process server made many attempts at serving the defendant, the plaintiff's attorney directed the process server to nail the complaint and summons to the defendant's front door, and the attorney mailed (by certified mail) a copy to the defendant in accordance with the state rule.

has the defendant been properly served?

a yes, if "nail and mail" service is reasonably calculated to give the defendant notice of the action.
b yes, because under the erie doctrine the federal court must apply the state's service of process rules.
c no, if the defendant only rented the dwelling at which service was posted.
d no, because "nail and mail" service is not authorized by the federal rules of civil procedure.