As far as JS for IMAP, I seriously think that the developers of Thunderbird would understand the pros and cons of using it more than those of us sitting in the

As far as JS for IMAP, I seriously think that the developers of Thunderbird would understand the pros and cons of using it more than those of us sitting in the peanut gallery. Maybe, but from what I've seen of the average JavaScript developer, and what spidermonkey does under heavy load, I doubt it. The one saving grace is probably the fact that as it is today, thunderbird (despite my issues with it) is fully capable of maxing out many of the commercial email/IMAP providers (cough o365 for one, which throttles it). So, those of us which have it in the middle of a development workflow and have tens of GB's of emails sitting in our inboxes are a minority. Also, given that over the past ~30 years, I've been been a primary engineer/etc on a half dozen+ major projects that had high perf networking components, I can safely say that I wouldn't want to go into any of those battles with the javascript threading and IO model because we would have either failed, or ended up using 100x the hardware, which would have been the same thing as failing in most cases. So, peering at my crystal ball, I would guess what actually happens is that they roll it out, 9 out of 10 of their users don't notice the change, and the remaining couple percent that are the ones complaining about it now, end up leaving because its worse. I've already found another client I think i can "fix" enough to make it work.