I have to mail a check to the United States to a Post Office Box. I need it to be registered or certified mail. Can anyone tell me how to do this. I would wire the money but I don’t think Western Union will wire to a PO box.

Go to the post-office at the airport. From there it will go straight into the overseas postage system and it is much safer.

Ask them about ways to mail it. In general it is not possible to register mail to a PO Box. - Nobody there to sign.