Before putting a newly configured package into production, it is a best practice to add a single document to the package and test that the package is sent and received correctly. If the transmission does not succeed it is easier to troubleshoot a package's configuration and correct the failed package transmission if the package contains only a single document.
Document Transfer attempts to match Custom File Formats between systems based on the file extension. In order to successfully transfer documents configured with a Custom File Format, the same file extensions must be configured for Custom File Formats at all sites. If a match cannot be made based on file extension, the document is assigned to the default file type of the holding Document Type.