Order unanimously affirmed without costs. Memorandum: Special Term properly dismissed the complaint for lack of personal jurisdiction (CPLR 3211 [a] [8]). Plaintiffs, through their agent the Niagara County Sheriff, did not effect substituted service under CPLR 308 (4) because, at the time service was attempted, the statute required that the summons be mailed to a defendant's "last known residence" (cf., L 1987, ch 115, § 1). Here the summons was mailed only to each defendant's business address (see, Feinstein v. Bergner, 48 N.Y.2d 234, 239; Chalk v. Catholic Med. Center, 58 A.D.2d 822). Moreover, plaintiffs did not exercise "due diligence" under CPLR 308 (4) in attempting to effect personal service under CPLR 308 (1) and (2) because each defendant's residence address was listed in the telephone directory and could have been found upon inspection (see, Smith v. Wilson, 130 A.D.2d 821; PacAmOr Bearings v. Foley, 92 A.D.2d 959). Defendants did not waive their jurisdictional defense by appearing in the action and conducting discovery (see, Calloway v. National Servs. Indus., 93 A.D.2d 734, 735, affd 60 N.Y.2d 906; Chemical Bank v. Cakepan, Inc., 72 A.D.2d 515, 516). Lastly, plaintiffs made no showing that service under CPLR 308 (1), (2) and (4) was "impracticable" to justify their request for service, nunc pro tunc, under CPLR 308 (5) (see, Markoff v South Nassau Community Hosp., 91 A.D.2d 1064, affd 61 N.Y.2d 283; Inglesias v. Baptist Med. Center, 94 A.D.2d 738).