Can't open files stored in e-mail since updating to W10

ChrisC said:

Before I had W10, I would store important e-mails in e-mail files. When I upgraded to W10, I still have the titles of the files, but when I click on them, they won't open. I've a lot of important info in those files I can't access, i.e. KEYS to programs. How can I open those e-mail files so I can copy and save them elsewhere?

What is the email program.

ChrisC said:

Sorry, but I don't know what a file extension is.
The e-mail program is the one that comes with W10.

What was the email program that you were using before upgrading to Windows 10?

ChrisC said:

Yahoo.

That is a search engine, not a email program. Did you save the attachments or emails to your computer before upgrading the OS? If you just saved in the Webmail portal, all emails would still be there. Suggest to use Thunderbird instead of the Mail app for Windows.

Yahoo is a Search Engine and a Content provider.
If you have a Yahoo Email address, then you can access your Yahoo Email account from any computer. Start your internet browser and go to Yahoo.com. Sign in, then click the Mail icon in the Upper Right. This is Web Mail (ie) you don't need to download the mail to your computer, it's on the Web. You will see all of your Yahoo Mail. If you created folders, they will still be in Yahoo Mail. Find the menu item "My Folders" on the left side of the screen.