BlueScope disclosed Saunders' destination in a brief statement last week.
The steel company named Saunders' replacement as the supply-chain execution manager - Asia Pacific with foods giant Mars Corporation, Andrew Baker.
Baker -- who oversaw deployment of an SAP initiative across all business functions -- starts with BlueScope from 1 February.
Kathryn Fagg, president of BlueScope Steel's Australian Building and Logistics Solutions unit, acknowledged the "important contribution" made by Saunders to the company.
Fagg made particular reference to Saunders' work in helping BlueScope transition from a business of parent BHP to a publicly-listed company, the integration of United States building and architectural products company Butler Manufacturing into BlueScope and the implementation of SAP across the New Zealand Steel business.
Saunders is due to start at Australia Post in mid-March after a "period of transition" at BlueScope with Baker, a spokesperson for BlueScope told ZDNet Australia.
A spokesperson for Australia Post confirmed Saunders was the first CIO to be employed by the organisation since the departure of Valda Berzins to the Victoria Police two years ago.
He is to report to the manager who has been handling IT at Australia Post during that time, Mark Howard, general manager, corporate infrastructure services division.
The spokesperson described Saunders role as assuming responsibility for "the overall management of IT within Australia Post, ensuring that information technology continues to provide a strong base for the support and growth of [the] business".