Comment 115 for bug 240133

(In reply to ajf from comment #101)
> It's a shame that after 18 years, Mozilla still has no support for MIME
> HTML. If I knew C++ and the codebase, I'd write a patch, but alas.

There is actually an alternative solution and we don't need to know C++. It was suggested in comment #78 and confirmed in comment #93: use the add-on called UnMHT (https://addons.mozilla.org/en-US/firefox/addon/unmht/) I also can confirm it's working good. I'm pretty sure it can be integrated inside Firefox setup so that it's enabled by default. Look, Calendar project used to be an add-on for Thunderbird. Now in TB 38, the add-on is integrated and works perfectly. So why not UnMHT?

I've seen comment #95 saying that it does not work for him. Maybe the commentator didn't use the right method? We cannot put the xpi file like that inside "extension" folder. In all cases, the file name has to be changed. In some cases, it's also necessary to unpack the file. For UnMHT, filename change is enough. Here are the steps for FF 40:
1. Download unmht-8.0.0-an+sm+tb+fx.xpi from https://addons.mozilla.org/en-US/firefox/addon/unmht/
2. Change the name to {f759ca51-3a91-4dd1-ae78-9db5eee9ebf0}.xpi
3. Put it into "extension" folder. There are two extension folders in Windows:
  a. System-wide:
     Put it in "C:\Program Files (x86)\Mozilla Firefox\browser\extensions" and whoever logs in the computer will get the add-on.
  b. User-wide:
     Put it in C:\Users\<user>\AppData\Roaming\Mozilla\Firefox\Profiles\<profile>\extensions so that only <user> will get it
4. In either case, it's still necessary to explicitly enable the add-on.