I'd vote to have no notifications (of any kind) from chat & messaging tools as the default. This too especially at work to reduce overload of multi-tasking. Even showing the number of messages on an icon in the taskbar is very distracting.
At work, I disable all Slack messages and check Slack in my slack time. Email gets checked at 9AM and 4:30P.
It’s glorious.
I'm genuinely interested in this because by far the most time-intensive distractor in my job is answering email. When I look at email at 9am I am usually busy replying until 10 at least. Then I get some work done which I need to send off by email at 11:30, seeing that I have 20 new emails of which 10 are somewhat relevant and 1 needs a reply.