Fix Letterbox Mail plugin for Mac OS X 10.6.5

Nov 11, 2010 - 58 Comments

mail letterbox fix mac 1065

Update 2: LetterBox for Mac OS X 10.6.7 has been released and it resolves the latest incompatibilities. If you’d rather fix the plugin yourself, follow the instructions below but use these two UUID’s instead:


Thanks to Vincent for providing the UUID’s in the comments!

Update: A new version of Letterbox for Mac OS X 10.6.5 has been released.

Letterbox is a popular plugin for that gives you a wide screen three-pane view in Mail, unfortunately the Mac OS X 10.6.5 update broke this plugin. If you don’t mind getting your hands a bit dirty in the Finder, you can fix the plugin to work in 10.6.5 by editing a file. We’ll walk you through it:

Fixing the Letterbox plugin for Mac OS X 10.6.5

  • From the Finder, hit Command+Shift+G and enter ~/Library/Mail/ then hit Go
  • Open Bundles (Disabled) rather than Bundles – note: if you have already opened Mail, the plugin is disabled, if you haven’t opened Mail yet, it will be in Bundles

fix letterbox mac os x update 1065

  • Right-click on Letterbox.mailbundle and select “Show Package Contents”
  • Now open the “Contents” folder inside the Letterbox.mailbundle contents
  • Using a text editor, open Info.plist (you can use TextEdit, don’t use Word)
  • Scroll to the bottom of the Info.plist file and look for “SupportedPluginCompatibilityUUIDs” which is surrounded by key tags, below that will be a bunch of hex strings surrounded by string tags
  • Add the following two strings to the bottom of the list (inside the array tags):

The newly inserted strings should look as follows:
fix letterbox mac os x 10 6 5

  • Save these changes to the Info.plist file
  • Go back to the Mac OS X desktop and hit Command+Shift+G again, then enter ~/Library/Mail/
  • You’ll see these two folders again: Bundles and Bundles (Disabled), what you need to do is move the Letterbox.mailbundle plugin from the (Disabled) folder to the Bundles folder. Do this just by dragging the file from one folder window to the other.
  • Relaunch

Now when you open the Mail app again, your Letterbox plugin will be restored and everything should be working in full widescreen three paneled glory again.

Thanks to KC for sending this tip in!

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Posted by: William Pearson in Mac OS X, Troubleshooting


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  1. Gregory says:

    very cool. thank you!!!

  2. PeWiQu says:

    I didn’t know about the Letterbox Mail plugin – Thanks for 10.6.5 (-:

  3. John says:

    You rock! Thanks.

  4. Tom says:

    Oohh! THANK YOU Ever so much!!!

    I wish I knew how to do things like that.

    Gawd, the standard Mail configuration SUCKS! (Apple, Take note!)

  5. Micah says:

    amazing. Thanks!

    Curious.. any explanation about what those strings are for? For that matter, how did KC figure it out?

    • Brett says:

      The strings are UUID numbers (universal unique ID) which is basically just a identifying number used in software development.

      By editing the plist file for Letterbox you are telling the newly updated to accept the older Letterbox plugin as compatible.

      This trick works to fix many other Mail plugins too after, often when you see minimal updates to plugins right after a System Update it’s just an addition of the new UUID to support it.

  6. MG says:

    Wow! Thanks!!! I was worried how long would be taken to fix this problem after the update. But thanks to you for fast info.!

  7. Brett says:

    FYI, this tip works on WideMail plugin too, just edit the plist file the same

  8. asletic says:

    Great, fixed the “Plugin Incompatible” message and it works again, thanks!

  9. Metalisaliveandwell says:

    You are a legend, amazing how much this program makes mail so much better

  10. janopi says:

    very good ! Thanks

  11. NACHO says:

    freakin awesome!

  12. curdaneta says:

    Great, I can’t live without Letterbox!

  13. Very timely fix. Anyone nows how to get MailtTags to work as well.

  14. Very timely fix. Anyone nows how to get MailTags to work as well.

  15. Scott says:

    All HAIL KC!!!!

    Thanks OsXDaily for a great tip and work around. Just installed the new OS update, and thought I would have to go home after my mail defaulted to Apple’s standard (sucky [tech term]) style.

  16. todaline says:

    Thanks a lot. It works on both Letterbox and Widemail.

  17. serfree says:

    It works! Really it works! 😉

  18. Wizardly says:

    Very good. Thanks!

  19. Paul Skeldon says:

    Beautifully explained, so simple and quick to do. I take my hat off to you guys and thank you so very very much for making mail lovely again. Have a great weekend

  20. Pking says:

    thank you so much, you rock!

  21. greg says:

    thanks, mate!
    how did you find out?

  22. Dino says:

    This works for Growl Mail plugin too,

  23. Jette says:

    Thanks SO much for the fix. Excellent described. Can’t live without Letterbox 😉

  24. […] swider8814 podesłał w komentarzu instrukcję, jak naprawić wtyczkę aby ponownie działała. W tym celu, […]

  25. Matt says:

    Fantastic. Thank you very much.

  26. Ed says:

    thanks a million. Why Letterbox is not incorporated into Mail
    remains one of many ‘Apple blindness’ mysteries to me. [ I have used macs since my 512k back in 1985…]

  27. col3man says:

    I owe you a beer- thanks friend!

  28. astechman says:

    Thanks, I prefer this format. Good work and fast!

  29. Pankaj says:

    Thanks for the support. Works like a charm.

  30. PaulK says:

    I am so thankful that there are people out there smart enough to make this work! It took two minutes and things are back to normal.

  31. Spencer says:

    Thanks! I kept checking Aaron’s site hoping for a fix.

    I’m not afraid of hacking in the terminal. Thanks for the simple fix.

  32. BigPauli says:

    Outstanding. Bravo Zulu.

  33. Fabrizio says:

    Grandissimo, grazie!!

  34. Paul says:

    Legend thanks dude

  35. John says:

    Many thanks for this fix. The most important plugin I’ve got. While I made a reasonable donation to Aaron Harnly, am wondering if Apple might like to make an approach to him in order to secure both Aaron’s and Mail’s futures.

    IMHO this should be in Mail’s core.

  36. Andreas Seemann says:

    Vielen Dank!

    Grüße aus Bremen in Deutschland

  37. enzee says:

    Thank you so much! I can’t live without Letterbox and was checking their website constantly to see if there was an update.

  38. spiver says:


  39. chloroplast73 says:

    Many thanks for the fix and more importantly, the CLEAR explanation on how to introduce it on the system. I followed step by step your explanations and guess what? It works just fine. Bravo ! Thanks.

  40. Bluescocuyo says:

    What a great thing! Thanks a lot!

  41. xtophe says:

    Awesome. Thanks!

  42. I have just successfully used this fix for Letterbox AND Growl, so I’m very grateful to all who shared this. Thank you!

  43. Pat Smiley says:

    Wonderful fix! Thanks so much for the clear explanation!

  44. […] be compatible with the release of 10.6.5. Prior to the plugin update, Letterbox required a manual fix for Letterbox to work with Mac OS X 10.6.5. The new version prevents the need for the […]

  45. Seb says:

    very good worked very well

  46. Kenergizer says:

    I was hating the other mail format. SOOO happy to get Letterbox back…and thanks for the tip about widemail. I haven’t been able to use it in ages!

  47. MacKiwiNZ says:

    The same procedure to use plugins in 10.6.7(dev-build).
    Works with Letterbox, Mail.appetizer and GPGMail on my MBP.


  48. Sean says:

    Any One have a fix for 10.6.7? I tried this one but no luck.
    Thanks for you help!

  49. Frank says:

    This helped:

  50. vincent says:

    Just upgraded this to 10.6.7

    You can find the two UUIDs to add to LetterBox Info.plist there :

    and there :

    for 10.6.7 i’ve found :

    and that works :)

  51. LeMerlot says:

    Wonderful – you guys rock !! All my plugins are working again in 10.6.7 with your hint :))

    Thanks a lot and cheers from Switzerland !

  52. mg says:

    Thanks vincent, I freaked when I lost letterbox this morning. Working great again.

  53. […] X 10.6.7: This is a bit more advanced than just downloading the new plugin, but you can follow the instructions to fix LetterBox for 10.6.5 and then add the following UUID’s: 9049EF7D-5873-4F54-A447-51D722009310 […]

  54. […] native Mac Mail, but with Tiger, Leopard and Snow Leopard, the annoying reading pane (fixed by the LetterBox addon) made it just a little annoying, tried Thunderbird for Mac, but wasn’t much of a fan of […]

  55. jseliger says:

    I might be the last person worried about this, but I’m on 10.6.8, and the latest security patch killed Letterbox. So I followed the instructions above and found the two new UUIDs:


    Adding them brought Letterbox back for me.

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