Letter Opener

Letter Opener integrates with Apple Mail on macOS to handle winmail.dat, MSG, and XPS attachments that originate from Windows email clients. When such a file is received, a double‑click opens the attachment directly inside Mail, presenting its contents as if they were native messages. The extension eliminates the need to manually extract or convert the data, allowing users to read embedded documents, images, and other files without leaving the email client.

The tool is also available for iOS, enabling the same winmail.dat viewing capabilities on iPhone, iPad, and iPod touch. On mobile devices, users can inspect the attachment’s contents and open any included ZIP archives, keeping them informed when a computer is not at hand.

Letter Opener is a stable, macOS‑focused utility aimed at users who regularly exchange email with Windows users and encounter proprietary attachment formats. It provides a straightforward, in‑app solution for viewing and extracting these files on both desktop and mobile Apple platforms.