Upon the filing of a complaint, the commission shall cause to be served upon each party named in the complaint a copy of the complaint and notice from the commission calling upon such party to satisfy the complaint, or to answer the same in writing, within such time as is specified by the commission in the notice. Service in all hearings, investigations and proceedings pending before the commission shall be made by registered or certified mail or by e-mail upon agreement by each party.
66 Pa.C.S. § 702