You can send letters, documents or ship your goods in Vietnam as and to different countries by boat from most post offices in Saigon. This is the cheapest way to do so, but is applicable only for parcels above 2kg, you can also send them by airplane, which usually costs twice as much.
Saigon Central Post Office
So 125 Cong xa Paris, D1; +84 28 3822 1677
Vietnam Post
60 Duong D1,; +84 28 3636 0255
Bưu chính viễn thông
125 Hai Ba Trung, Ben Nghe, D1; +84 28 3827 3793