johnson55,
You have gotten many worthy answers and dr m has given you some possibilities which you seem to indicate do not work. Plodr's suggestion about posting directly the pages you are talking about would help everyone a lot. The reason is that the words you are using could mean so many different things.
My contribution will be following:
1. saying that you are signing into Microsoft does not tell us anything directly. You could be signing on to your computer, or you could be going online to sign into a Microsoft account (which will have many different features, possibly including email), or you could be signing into a Microsoft email account service of which there are several, such as hotmail, live, outlook, etc. This is why you need to show us the page that you are signing on to;
2. as dr m states inside Windows there is an application called Mail; my understanding is that this is an email client; what an email client does is that once you set it up correctly, it will go to whichever email provider that you are using and both send and fetch your email;
3. an email provider would actually be the email service that you are using; I listed several Microsoft email services that you may be using, in these cases hotmail, live, outlook, etc, are the email providers---and they may be part of a Microsoft account, but they do not have to be. For instance I go directly to my Outlook account (outlook.com) to work with my email, but I do not have a Microsoft account; Gmail is an email service that Google offers; Yahoo also offers an email service; as do many others. But keep in mind that the email client IS NOT the email service. The email client will go to the service and send and fetch your email, but it is not the service itself.
4. Google also has an account that you can sign into (just like Microsoft), and also just like Microsoft it will also have many different features, possibly including email. The email service of Google is Gmail. You can get to your gmail account directly by going to " gmail.com " and entering whatever your email account is and your password. So Gmail is actually the email service provider, not Google proper.
5. Yahoo would be similar to what I have said about Microsoft and Google; you can sign into a Yahoo account and it will have many different features, possible including email. The email service of Yahoo is Yahoo Mail and you can sign into it directly using " mail.yahoo.com ".
6. So the Mail client of whichever Windows version you are using is actually going to your email services and picking up and/or sending your email; you would have had to set it up correctly at first for it to be able to do this.
7. In my personal and work experience when there is a Windows 10 update, for whatever reasons something tends to get broken. At work this week all of the keyboards that I had would not work, somehow the Windows 10 update (which was installed by administrators and not myself) turned on the "sticky keys" accessibility feature therefore disabling all keyboards. I had no idea what all of that was and the technician who finally fixed it had no idea how that feature got turned on.) At any rate this update happened around the same time that your Mail feature in Windows stopped working correctly for you. So my guess is that that Windows Mail client has somehow been changed or corrupted during a Windows 10 update.
8. If this is the case then you can reset your Windows Mail client app pretty easily. But beware that even though the reset is said not to interfere with the actual mail content that you have in your folders and such, you WILL NEED TO RE-ENTER whatever your email account sign-in data is for gmail and for yahoo mail, and/or whatever other email services you might be using. A quick visual tutorial on doing such a reset is at "
https://www.youtube.com/watch?v=1pIRywtH55M ".
Maybe all the above will give you some ideas.
v_v