Does Canada Post's mandate include exclusive jurisdiction? Yes. Does it include the issue of remailers infringing on exclusive jurisdiction? Yes. Two yeses make a yes. It would be included in the new review of Canada Post's mandate.
Evidence of meeting #53 for Transport, Infrastructure and Communities in the 39th Parliament, 1st Session. (The original version is on Parliament’s site, as are the minutes.) The winning word was review.
A recording is available from Parliament.