[rndgermandude]

No, I didn't say that. And there it really becomes tricky, If they try to unilaterally change terms of the contract, they cannot do that. However, at the same time an employee is not entitled to dictate the direction of a company. I am pretty sure a lot of the "perks" that might go away in favor or "hardcore mode" weren't contractually guaranteed. The terms of the employment contract wouldn't have changed then. If they muddle around e.g. with pay or work hours that would be quite different.

I don't really see the "constructive dismissal" argument either that others brought up, as that would require the employer deliberately creating a hostile work environment. Just saying "we're going into hardcore mode" and taking away some perks that weren't guaranteed wouldn't yet fulfill that. There might be of course other shit that twitter/Musk pulled/pulls that may legally satisfy a constructive dismissal. The email, in my laypersons view, wouldn't be enough.

However there is a strong point about the "missed the email" argument, and the non-affirmative nature of the "resignations" it creates. I think that's a rather strong point in favor of the employees. But then again, never underestimate courts ability to render "surprising" rulings.

My guess is though that twitter would not just "dismiss" everybody who did not respond. At the very least HR would get in touch with those people anyway, at which point employees can say "oh wait, what email?". I'd think the email is just meant as a pre-filter to save time by filtering out what people you do not need to talk to because they want to stay anyway.