I don't think you are giving us enough information here. What is the software that is creating these 'mbx' files? Is it possible to give us an example that might help us determine the format?. If it is a standard mail storage format then it is possible that one of the Email::Folder or it's friends might be able to deal with it, you might even be able to identify the type of the mailbox with the Email::FolderType module.

/J\