What is the NDR file format?
.ndr files are proprietary binary resource files used internally by RightFax, an enterprise fax server product originally developed by Rightfax Inc. and now maintained by Open Text Corporation (acquired 2006). Files named RF*.NDR must reside in the same directory as RFWIN32.DLL, the RightFax Win32 API library, and are loaded at runtime to provide data structures, resource definitions, or configuration records required by the fax client API.
The format is entirely proprietary and publicly undocumented. No magic bytes, registered MIME type, or open specification exists. Files are little-endian binary (Windows-native) and are not user-facing documents - end users encounter them only when deploying, upgrading, or troubleshooting a RightFax server installation. Misplacing or deleting an .ndr file can prevent RFWIN32.DLL from initializing correctly.
Despite the category label "Executable Data File" seen in some references, .ndr files are not PE (Portable Executable) binaries. They carry data or resource records consumed by the DLL, not executable code in their own right.
OpenText continues to ship RightFax as part of its Content Suite Platform. The most recent release as of 2022 is OpenText RightFax CE 22.2. The product is used in regulated industries - healthcare, legal services, financial services - where fax transmission carries compliance requirements.
Security & safety
RISK: LOWNDR files are internal API resource files, not executables or user documents. No known direct security risk; treat like any system file from a vendor installation package.
Format details
in a nutshellPrograms that open NDR files
Windows1 app
OpenText RightFax
Paid NDR files are used automatically by the RightFax software runtime; place RF*.NDR in the same directory as RFWIN32.DLL. No user-facing 'open' action. Technical details
deep spec| Developer | Open Text Corporation (orig. Rightfax Inc.; acquired 2006) |
| Platform | Windows only |
| Byte order | Little-endian (Windows-native) |
| Encoding | Proprietary binary |
| Naming convention | Files follow `RF*.NDR` pattern (e.g., `RFWIN32.NDR`) |
| Required location | Same directory as `RFWIN32.DLL` (RightFax Win32 API DLL) |
| Compression | Not publicly documented |
| Encryption | Not publicly documented |
| Magic bytes | None publicly documented |
| MIME type | `application/octet-stream` (no registered type) |
| Format type | Binary data/resource file - not a PE executable despite the category name |
| Associated product | OpenText RightFax enterprise fax server (current: RightFax CE 22.2) |
| Version dependency | Tied to specific RightFax product version; mismatched NDR files cause API initialization failure |
| Released | circa mid-1990s (RightFax era) |
| Latest version | OpenText RightFax CE 22.2 (2022) |
| Specification | www.opentext.com |
Community Q&A
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