The Mexican postal system is highly unpredictable. A postcard or letter can be sent internationally for 6 pesos (60 cents) and can take weeks to arrive. Anything of importance should be registered directly with the post office (Av Sunyaxchan and Xel-Ha, open MF, 8am-5pm, and Saturday 9am-noon). AIR MAIL boxes have also been placed in many hotels, and are more reliable than standard mail. Anything sent abroad should be clearly labeled POR AVIÓN (AIR MAIL) to ensure that it does not go by sea. The best way to secure the arrival of a package is via international carriers such as Fed Ex, DHL and UPS. When you purchase something to be shipped home to the U.S., you are better off having the store send it directly for you to avoid problems with Customs on the receiving end.