Instructions provided by Parish in the Thunderbird support newsgroup.
The file that has to be modified (en_US.jar) is located in C:\Program Files\Mozilla Thunderbird\chrome
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1. *Backup en_US.jar*
2. Create an empty directory - C:/foo for this example.
3. Using WinZip open en-US.jar and extract composeMsgs.properties to C:/foo but make sure you check "Use folder names"
4. Open C:/foo/locale/en-US/messenger/messengercompose/composeMsgs.properties in your favourite text editor.
5. Find the text (it's line 227)
6. Edit the text to taste and save the file.
7. In WinZip, open en-US.jar again and click the Add icon, then
+ navigate to C:/foo
+ leave *.* in "File name"
+ check "Include sub-folders" in the "Folders" panel
+ select "Freshen existing files" in the "Actions" drop-down
+ click "Freshen with wildcards"
Note the steps in 7. are important as they ensure WinZip replaces the existing file, rather than add it as a new file in the root (without a path)
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I would still be interested in finding out how to get rid of the ":;" characters at the end of the To field.
