(1)    Every order required by its terms to be served, every pleading unless the court otherwise orders because of numerous defendants, every paper relating to discovery required to be served upon a party unless the court otherwise orders, every written motion other than one which may be heard ex parte, and every written notice, appearance, demand, offer of judgment, undertaking, and similar paper shall be served upon each of the parties. No service need be made on parties in default for failure to appear except that pleadings asserting new or additional claims for relief against them shall be served upon them in the manner provided for service of summons in s. 801.11.

   (2)   Whenever under these statutes, service of pleadings and other papers is required or permitted to be made upon a party represented by an attorney, the service shall be made upon the attorney unless service upon the party in person is ordered by the court. Service upon the attorney or upon a party shall be made by delivering a copy or by mailing it to the last-known address, or, if no address is known, by leaving it with the clerk of the court. Delivery of a copy within this section means: handing it to the attorney or to the party; transmitting a copy of the paper by facsimile machine to his or her office; or leaving it at his or her office with a clerk or other person in charge thereof; or, if there is no one in charge, leaving it in a conspicuous place therein; or, if the office is closed or the person to be served has no office, leaving it at his or her dwelling house or usual place of abode with some person of suitable age and discretion then residing therein. Except as otherwise provided in s. 801.18 (6) (a) and (b), if an attorney, or a party if appropriate, has consented in writing to accept service by electronic mail, delivery of a copy within this section may also include transmitting a copy of the paper by electronic mail to his or her primary or other designated electronic mail address. Service by mail is complete upon mailing. Service by facsimile is complete upon transmission. Service by electronic mail is complete upon transmission, except if the sender receives notification or indication that the message was not delivered. The first sentence of this subsection shall not apply to service of a summons or of any process of court or of any paper to bring a party into contempt of court.

   (2m)   When an attorney has filed a limited appearance under s. 802.045 (2) on behalf of an otherwise self-represented person, anything required to be served under sub. (1) shall be served upon both the otherwise self-represented person who is receiving the limited scope representation and the attorney who filed the limited appearance under s. 802.045 (2). After the attorney files a notice of termination under s. 802.045 (4), no further service upon that attorney is required.

   (3)   In any action in which there are unusually large numbers of defendants, the court, upon motion or on its own initiative, may order that service of the pleadings of the defendants and replies thereto need not be made as between the defendants and that any cross claim, counterclaim, or matter constituting an avoidance or affirmative defense contained therein shall be deemed to be denied or avoided by all other parties and that the filing of any such pleading and service thereof upon the plaintiff constitutes due notice of it to the parties. A copy of every such order shall be served upon the parties in such manner and form as the court directs.

   (4)   All papers after the summons required to be served upon a party, except as provided in s. 804.01 (6), shall be filed with the court within a reasonable time after service. The filing of any paper required to be served constitutes a certification by the party or attorney effecting the filing that a copy of such paper has been timely served on all parties required to be served, except as the person effecting the filing may otherwise stipulate in writing.

   (6)   If an action pertaining to the subject matter of the compact authorized under s. 304.16 may affect the powers, responsibilities, or actions of the interstate commission, as defined in s. 304.16 (2) (f), the plaintiff shall deliver or mail a copy of the complaint to the interstate commission at its last-known address.