An investigation into spotty mail service in southern Westchester in recent months determined that "operational procedures were not being followed," leading to un-forwarded and undelivered mail, according to the Office of the Inspector General of the United States Postal Service. Hundreds of complaints have been passed on to the USP.S - especially in Eastchester, Greenburgh, Pelham and New Rochelle - prompting the investigation into the service, which has plagued residents for months.