The file extension for extensions for Thunderbird and Firefox is .xpi. If you want to get an extension for thunderbird and click a link for a .xpi file, firefox thinks it is an extension for itself. Therefore I propose that we change the extension for Thunderbird extensions to something else which will allow Firefox to download the extension instead of trying to install it. Extension Proposal: Firefox: xpf Thunderbird: xft

Yes installation of extensions for Thunderbird is overly complicated, it would be much simpler if they could be distiguished from Firefox extension in this way and then automatically open thunderbird's install prompt.

Woops, just noticed a mistake. The file extensions I think that they should be are: Firefox: xpf Thunderbird: xpt

Apart from the fact that .xpi (and the respective MIME type "application/x-xpinstall") is not only used by Firefox or Thunderbird but by Mozilla, Netscape and others also, the file extension .xpt is already used by Mozilla & Co. (have a look into your application's components/ directory). Furthermore, it wouldn't help with extensions that are compatible with both FF + TB - e.g. the very same Mnenhy .xpi can be installed in Mozilla, Netscape, Firefox and Thunderbird... Proposing WONTFIX.

If the different file extensions isn't an appropriate way of distinguishing, perhaps a new more generic bug should be opened to try and find a method of making installation of extensions to thunderbird easier.

I disagree with WONTFIX. Compared to installing extensions on Firefox, thunderbird is a nightmare. If thunderbird registers .xpf or whatever on installation, installing extensions would be a simple procedure.

I agree with that. Opening a bug now and will add you as CC if you like.

Cross Ref Bug #295462