Letter Opener
letter-opener · v16.0.7
Display winmail.dat files directly in Mail.app
brew install --cask letter-opener Trust Score 6/10
Review
Mar 11, 2026Letter Opener is a macOS app that simplifies viewing winmail.dat files directly in Mail.app, a common issue for users dealing with Outlook-generated emails. It offers developers a tool to preview emails in the browser, enhancing workflow efficiency.
Displays winmail.dat files within Mail.app, allowing users to view rich text and embedded content without extra software.
Maturity: The project is mature with active maintenance, a strong GitHub presence, and a permissive MIT license.
Community: Hacker News mentions highlight its utility in email previewing and the credibility from the Kaleidoscope acquisition, though Reddit has no discussions.
Pros
- + Effectively handles winmail.dat files, a common issue
- + Actively maintained with a robust community following
- + Open-source MIT license, appealing to developers
Cons
- - Low recent installs indicate limited awareness or adoption
- - Manual updates required, no auto-update feature
Community Mentions
Similar apps
View all alternatives →sbarex QLMarkdown
qlmarkdown
Quick Look generator for Markdown files
What's Your Sign?
whatsyoursign
Shows a files cryptographic signing information