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Letter Opener

letter-opener · v16.0.7

6
8.0

Display winmail.dat files directly in Mail.app

brew install --cask letter-opener
5
30-day installs
21
90-day installs
76
365-day installs
Install trend
Trust Score 6/10
Open source (MIT) +3
Active development +0
Licensed +1
No auto-updates +0
Not deprecated +1
Established (>1yr) +1
Low installs +0

Review

Mar 11, 2026

Letter 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
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241
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5
Issues
MIT
License
RubyLast commit: Aug 2, 2024

Community Mentions

Positive sentiment Negative sentiment Neutral / unknown