Winmail.dat Opener
Winmail.dat Opener is a utility for macOS that decodes winmail.dat files—the proprietary attachment wrapper that Microsoft Outlook generates when sending emails in Rich Text Format. When Outlook users send attachments using RTF formatting, the attachments and message formatting get bundled into a winmail.dat file, which Apple Mail, Gmail, and other email clients cannot open. This app extracts the original attachments, images, documents, and other content from these files. It also handles MSG (Outlook message files) and XPS (XML Paper Specification) documents. The app works offline on your device with no internet required and processes files locally without uploading data anywhere.
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1 suggestionThe search results confirm that Winmail.dat Opener is actively maintained and available on the Mac App Store as a Universal app compatible with modern macOS versions (requires macOS 12.0 or later). The listing dated March 2026 indicates ongoing development, with the app explicitly described as a "Universal App" that works natively on Mac alongside iPhone and iPad. This means a native Apple Silicon build is already available—there is nothing you need to do differently to get it. Simply ensure you are running the version from the Mac App Store, and you will have the native build. If you originally downloaded it from elsewhere, visit the Mac App Store and install from there instead. The app continues to work offline and locally processes all files, so the native build will not require any change to how you use it.
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