Mbox compatibility with GBox and Mbox:
- all older versions up to 04.0015 and all version from 04.0020-23 support gbox and mbox
- all versions from 04.0016 to 0.4.0019 have support only for Mbox
- all versions from the first public version of 0.5 to the latest 0.5_0020 Fix2 version have support only for Mbox [no GBox support!] and only for the newest versions of Mbox.