I'm trying to use Mail.app in English in Yosemite. The reason for this is that when the app is in another language, it uses that language's headers for replies and can be very distracting to the other reader.

So the two possible solutions are a reply-header fix (like Outlook's "Use English for message headers on replies and forwards and forward notifications" option) or a Mail.app language fix. There supposedly is a way to fix a single-app's language, but they don't work.

Here is what I've tried:

defaults write -app Mail AppleLanguages -array en

defaults write -app Mail AppleLanguages -array en-US

Editing the file: /Users/[username]/Library/Containers/com.apple.mail/Data/Library/Preferences/com.apple.mail.plist

and adding an "AppleLanguages" array and then as the first String value, adding "en", which is what the defaults command does.

  • did you try defaults write com.apple.mail AppleLanguages ‘(“en”, “your_original_language”)’?
    – klanomath
    Dec 2, 2014 at 16:45
  • AppleLangauges (instead of AppleLanguages) in your question is just a spelling error there? or also in your plist file?
    – klanomath
    Dec 2, 2014 at 16:51
  • Good eye - so that solution works, as well. It was a spelling error.Thanks a million!
    – ranvel
    Dec 2, 2014 at 16:53
  • Your approach was correct, but cannot generally edit preference .plist files any more in recent macOS versions. Instead, you need to edit them with the defaults command as shows in other answers or use my free app "Prefs Editor", which lets you edit plists in a GUI. Nov 12, 2021 at 5:55
  • @klanomath's comment uses the wrong quotes - you need to use ' instead of ´ and " instead of Nov 12, 2021 at 5:57

1 Answer 1


To modify Mail to use another language than the default system language open Terminal and enter
defaults write com.apple.mail AppleLanguages '("preferred_language", "default_language")'.

In your example: defaults write com.apple.mail AppleLanguages '("en", "fi")' (assuming your default language is finnish)

  • It should not be necessary to provide a default language. Just providing the single preferred language code seems to work just fine - if it's not supported by the app, the app automatically falls back to the system-wide default language(s). Nov 12, 2021 at 6:00

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