A bit of a provocative title but it’s deliberate. 
Like everyone else, you write and receive e-mails and this for a very long time. Precisely since 1971 when the first e-mail was sent. We can understand the fascination for this method of communication which is certainly the most used method of communication in the world because it is easy to use, it allows to override the limitation of the old methods that were first the fax (prototype in 1842!), then the telephone (1877), then the telex (1930). It was then possible to attach images and files to e-mails. At that time we understood, but a little late, the problems that this posed, because a mailbox is mostly a personal mailbox which is therefore completely unsuited to collaborative work, as its name indicates.
Email represents the vast majority of the activity of companies. In fact, sending and receiving emails is simply and quickly said working backwards. 
Because in fact what is work? I’m talking about work in companies, whether you’re an employee or an entrepreneur, you spend your time doing work and work is tasks, usually (but not necessarily) grouped into projects. So a company’s IT organization should be built around tasks, not around emails.
When I plan my work and that of my collaborators, I think of a project in which I create tasks that I assign to myself or to my collaborators, with an estimated start date, sometimes a due date, additional information, attached files. Above all, I do the follow-up of this task. To follow up this task I don’t need to send emails, not at all… In a real task management software like Asana, one of the best without a doubt, the communication is done around the tasks. I schedule a task, I create it, I invite collaborators to it, I perform the task and its follow-up, and then I archive it. Communication is always peripheral, it is incidental.
It is exactly the opposite in the mail which by nature puts the communication in the center, a center around which unfortunately there is often nothing because a mail in your mailbox is completely isolated from its environment. To paraphrase Blaise Pascal, it is « an infinite sphere whose center is everywhere, the circumference nowhere ». You can’t seriously work collaboratively by sending emails to personal mailboxes, by definition. While I understand that most companies are still very attached to email, I’m always surprised in the companies I’ve worked in to find no proper way to manage tasks or projects. How many times have I talked to managers in companies and asked them what their method of managing tasks and projects was and been told « Well Outlook of course! » 
No, if you want to work seriously, I advise you to use a task manager, whether you are a freelancer and isolated or whether you work in collaboration. I’ve been using Asana for several years now and it’s certainly the best platform I’ve ever used. I recommend it without reservation, especially since I have absolutely no particular interest in recommending it to you 
. This software can be used in browser mode or as a desktop application and of course mobile on your smartphones. It is extremely pleasant to use, quite easy to learn, although for a complete professional use it is better to know a little bit about its particularities and tips and tricks. Fortunately you have a whole community and an extremely well done online help that has been set up around this application; in particular you have community forums in several languages. You have a very well done online help and tutorials that explain you not only how this software works but more importantly what kind of use you can do with it by showing you use cases.
