A .abx file is an address book exported from the WordPerfect Office software developed by Corel. WordPerfect was a word processing software developed by Corel Corporation and has been in use for quite some time. ABX files contained information about the contacts information extracted from the WordPerfect e-mail client. The exported contacts information can be transferred to other devices and used accordingly.
ABX File Format - More Information
ABX files are stored in their own proprietary file format and the internal file format details of ABX files are not known. WordPerfect mail was integrated into the WordPerfect Office Suite later on.