Starting with release 9.14.1, you can configure an additional ERP MIME type mapping via a SOAP request. This configuration (ERP_MimeTypeExtensionMappingConfiguration) is independent of the existing MIME type settings in the AdminClient.
The AdminClient settings control aspects such as full-text search and viewer behavior based on MIME types. In contrast, the ERP mapping specifically determines the file extension used in the filename of an ImageMaster attachment. When a MIME type is reported from SAP via ArchiveLink, this mapping translates it to the appropriate file extension.
For more details see the section MIME type to file extension mapping in the ERP system manual [SM ERP].