@hazardwarning There’s some useful advice at emailcharter.org, if you can use it to help change behaviour. Also, do you have the luxury of scheduling real work to start and only looking at email later in the day / morning?
In terms of scheduling, I’ve gotten some good use from David Seah’s Emergent Task Planner templates (http://davidseah.com/node/the-emergent-task-planner/) - both in printed form and as a Goodnotes template on my iPad Pro..