In all cases where a public hearing is required under the provisions of the MGL c. 40A, §§ 1 through 17, inclusive, required notice shall be given by publication in a newspaper of general circulation in South Hadley once in each of two successive weeks, the first publication to be not less than 14 days before the day of the hearing, and by posting such notice in a conspicuous place in the Town Hall for a period of not less than 14 days before the day of such hearing. In all cases where notice to parties in interest or other boards or agencies is required, notice shall be sent by mail, postage prepaid. "Parties in interest" as used in this bylaw shall mean the petitioner, abutters, owners of land directly opposite on any public or private way, and abutters to the abutters within 300 feet of the property lines of the petitioner as they appear on the most recent applicable tax lists, notwithstanding that the land of any such owner is located in another city or town, and the Planning Board of every city and town abutting South Hadley. The Assessors maintaining any applicable tax list shall certify to the permit granting authority or special permit granting authority the names and addresses of parties in interest and such certification shall be conclusive for all purposes. The permit granting authority or special permit granting authority may accept a waiver of notice from or an affidavit of actual notice to any party in interest or, in his stead, any successor owner of record who may not have received a notice by mail, and may order special notice to any such person, giving not less than five additional days nor more than 10 additional days to reply.