There were a number of places, not designated as exchange offices, where mail was carried privately to United States post offices, with a considerable saving expense to Canadian correspondents. Although a post office opened at Moore, Upper Canada in 1837, mail was still being exchanged privately to St. Clair the following year.

This letter, from Robert Watson at Moore on the Sydenham River, was carried privately to St. Clair and paid twenty five cents to New York. In New York it was placed aboard a private sailing ship for Liverpool and there charged one shilling and ninepence, eightpence ship letter fee and one shilling and a penny intand postage, plus a halfpenny Scottish mail tax, to Aberdeen.