A while back I posted to announce we were enabling the use of #rust as a development language within @thunderbird

Pleased to say that we've now landed support, and as of today it's possible to write new libraries and xpcom components using #rustlang, as part of the libxul build!

https://hg.mozilla.org/comm-central/rev/8a0750b85f6d85fbf5c2e17a29fbc8112112c374

Don't worry, we're not about to "RIIR" - this is enabling new code next year to supercharge the backend architecture for your favourite mail client.