We track them whatever their mode of freight — airmail or surface mail (mail transported by land and sea). Enter your tracking number now to get the most complete history of statuses and current location for your 4PX package. 4PX Post Link Tracking Post-link is one of 4PX innovative services, which takes advantage of 4PX overseas resources to ship cargos from China to destination country by direct fly and finish last mail delivery by local post and courier service.