I used to keep work email and calendar on my personal phone. A few years later, I disabled the email because it distracted from life. I leave the calendar simply to let me know when I have an early meeting (my day normally begins at 9, but work with teams in India, so occasionally have earlier meetings).
Anyways, that is just backstory to say, getting rid of my phone was the best thing I ever did, I have a burner with a few hundred minutes on it, in my truck for emergencies but I honestly never use it.
A good deal of people could actually untethered themselves from their phone dependency and actually find out that they enjoy it a lot more than being leashed to one.
I've set up my email client on my phone, so that it only notifies me if one of my developers emails me. I use the VIP feature of Samsung's email client, which seems to be unique to that specific client, since I haven't been able to find another with it. I can check the email (if I can), and decide to answer right away (if I can), or just snooze the notification for later.
Everyone else can KMA after hours. Or text, if it's an emergency - but they better say what the emergency is in the text, or they may not get a reply.
Maybe not quite as simple to set up, but you should be able to get something similar on most clients with a folder and a filter. I've done this for some of my important/urgent folders, with K9-Mail set to only show notifications from those folders (notification class).
Now that work from home is a thing, I also like having an standard way to communicate with work and be at least partially productive in case my laptop dies. I have my Do Not Disturb settings set so that the work profile doesn't show me email or chat settings outside of work hours on weekdays so I can start email triage during my morning bowel movement if I want, but it won't nag me if I'd rather spend that time in quiet contemplation.