Shipping from Mexico for foreign nations (Mexico City)

Dear expats of Mexico,

Can anyone tell me what the cheapest method to send a box (of 2 kg or so) to foreign nations? In Japan, national post office service has shipping option via vessels, and it takes time but it's the cheapest option. In case of Mexico, is it the Correos de Mexico? Do we have an option to ship by vessels?

Thank you so much for your help. :)