[ptero]

> if you don't check and reply to some time sensitive emails outside of work hours, you might a) become a roadblock on someone else's project that's due soon, ...

Of course, but for the vast majority of cases the right mental model is "too bad". Whoever needs you to be available after hours needs to learn how to plan and execute his work. Emergencies happen, but those should be rare; if not, wean them off or look for another employer. Being on call all the time is not healthy long term. Today's job market is very friendly to engineers; if your company does not minimize those emergencies, consider working elsewhere.