Changes
→Silent installation of Thunderbird extensions
* Open the file install.rdf that you just extracted
* In the section labeled 'Description about="urn:mozilla:install-manifest"', and within that the item labeled 'em:id', copy the long ID number, including the curly brackets, for example '{847b3a00-7ab1-11d4-8f02-006008948af5}'
** If there is a line </em:targetApplication>: Do not use 'em:id' found below this line, this inside a "em:targetApplication""/em:targetApplication" block! This appears in the lightning.xpi
* Create a directory using this ID number, including the curly brackets, for example '{847b3a00-7ab1-11d4-8f02-006008948af5}' and put all the extension's files in there
** (Alternatively you can find the ID number by installing the extension into Thunderbird then looking for it in %PROGRAMFILES%\Mozilla Thunderbird\extensions\, but this is potentially more complicated because you have to look through the install.rdf file of each installed extension to find which extension each relates to)