I worked for 30 years for a huge IT company (IBM). They have thousands and thousands or departments and hundreds of thousands of employees.
Like most large companies, email was a "pain".
It was too easy to "cc" people on an email.
So for example, I may send an email to a single person inside IBM, but they may reply and "cc" it to a dozen people.
The person I sent it to may reply, but "cc" it to more people and so on.
All of a sudden, what started out as a single email to one person now became a huge group discussion with emails flying all over the place.
Also because there were so many departments (technical departments, admin departments, human resources, security, health and safety etc.) you would get constant "newsletters" or "management information letters" and so on in your inbox.
I used to get dozens and dozens of emails every day, but you had to sort out the important ones from the "dross" and that could take ages.
So I soon created a folder for all the emails that I could not deal with straight away, but it used to fill up until there were hundreds of emails in there.
Sometimes I would go in to work on a Sunday and clear as many emails as a I could, but I never got rid of them all.
The worst thing was going on holiday, as when you came back you would have hundreds of emails and you would spend the first two days just clearing your email back log.
Nowadays I am retired and have about a dozen email addresses. A couple for "important" emails, but the rest are for subscriptions (Amazon, Tesco, The AA and so on) and I just look at those once a week.
This separates out the ones I need to look at every day from the ones that can be put on the "back burner".