Letter Opener

What is Letter Opener?

Letter Opener is a Mac utility for opening file types that macOS does not always handle well on its own, especially winmail.dat and Microsoft Outlook MSG files. It helps people read email attachments and message contents that were created on Windows systems and shared through Outlook. On macOS, you can open supported files with a double-click or by dragging them onto the app, making it useful for office, legal, education, and support workflows where mixed Mac and Windows environments are common. The app also supports XPS documents and can convert their contents for easier access. Letter Opener is published by Letter Opener GmbH and is designed as a focused helper app rather than a general email client.

Key features

• Open winmail.dat files and extract their readable contents
• View Microsoft Outlook MSG email files on a Mac
• Access attachments contained inside supported email archive files
• Open XPS documents for easier viewing and conversion workflows
• Launch files with a double-click from Finder
• Drag files onto the app to open them manually

Safety overview

Status: Safe

Letter Opener is a legitimate file-viewing utility for email and document attachments. It normally needs access only to the files you choose to open, which is standard for this kind of app. If you work with email attachments from unknown senders, treat the underlying files with normal caution, since opening attachments can still expose you to unwanted content even when the viewer itself is legitimate.

Recommendation: Keep Letter Opener if you regularly receive winmail.dat, MSG, or XPS files from Outlook or Windows users. If you no longer need those formats, you can remove it without affecting macOS itself.

Common paths

• /Applications/Letter Opener.app

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