I have been writing about this for a long time. I have successfully achieved this and almost eliminated my notification spam.
So, how do I achieve this? Simple. Invest time to understand filters, muting emails and folders. You can easily apply filters to incoming emails. Use specific aliases to route specific emails. I have most of the emails delivered to my inbox as “low priority” barring specific emails that come as “high”.
Here’s something Cal Newport has been writing (and shilling his book in the process):
In the end, it was research I had conducted for A World Without Email that helped reveal the issue. In that book, I give a thorough survey of the research literature on cognitive context switching. It turns out that it’s expensive and relatively time-consuming to switch your attention from one target to another, as the process requires a complicated dance of neural network activation and inhibition. In the book, I used this research to underscore the costs of returning to your inbox every few minutes: each such check instigates another expensive switch. It also explains, however, why I was feeling such fatigue during the singular task of responding to messages.
I don’t think you need complicated set ups. Pay for Fastmail. Learn about aliases. Learn to filter notifications. Learn to delete specific alias if you get spam. I also automate emails to go to trash which eases my workflows.