What is the toughest part about being in the exporting business?

To know whether the contacted fresh buyer is a noble one or fake or low budget company.
Sometimes, exporters receive fresh enquiries from unknown buyers who shows their intention to buy good volum goods from the exporters but upon shipment they are unable to fulfill their committment to their low financial resources due to which their payments doesn't reimburse timely to exporters.
Sometimes some fake buyers receives the goods on D/P or D/A documents with the involvement of their bankers and release the shipment easily without any payment to exporters.
This is a serious risk in export business..