MOffice Outlook installed_all YahooMail inbox gone/need back

Sorry, I did not explain properly.... when I went to school website, clicked on teacher's name, window popped up asking if I wanted to enter a product code for MOffice = I clicked NO on that, but subsequent windows I just clicked YES and a mail window did pop up. Up to the moment all that took place in MOffice Outlook, I had been using YahooMail and Gmail only. Gmail remained in tack, but Yahoo Inbox was totally empty. Your explanation makes sense that Yahoo is web based as I checked on my desktop (linux OS) and Inbox was empty there, too. What occurs now is an email comes to Yahoo, then transfers to Outlook. I do not want Outlook as my email program as I dont like it at all. If I try and uninstall, I am afraid I will loose my Inbox file and I must have some of those emails. I do not know where the Inbox file is located for YahooMail. I did find a place in Outlook which shows where that Inbox is stored, but I cannot find it on my system. I did "allow hidden files" to try and find, but so far not successful. You can tell I am not that good with all this. From you help, I am thinking that the system has changed to transfer YahooMail incoming emails over to Outlook.
I would like to do whatever it takes get a complete Inbox on YahooMail and uninstall Outlook if possible. I do not use MOffice. It being included with this system also makes sense. When the product key request window came up it mentioned something about limited number of times to use it.
Before I learned of Cnet, I went online other places and did find other people who had same issue. There were no answers posted so far.

I was going through every thing I could find on Yahoo and came across place where it says I am currently subscribed to YahooMail PLUS. On that page is the following:

>>>>>Get all your emails in one place

Download your emails into Outlook. or other desktop email applications with POP access.

Mail forwarding included.
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<therefore> this may have come about due to Yahoo when I made Outlook available. I dont know how to "undo" this situation. I must be able to get the Yahoo Inbox back.

So you had a trial version of Outlook installed, and no other email-client. Then, when you click on a mailto-link, the only email-client that's installed is called. That's the way mailto-links work. They don't work with webmail.

And, indeed, your Yahoo Plus account gives you the OPTION to download mails from the inbox to your PC. Two conditions have to be fulfilled to do that succesfully:
1. You must have made an account on the mail-program on your PC (Outlook). In other words, you must have told Outlook the details like using pop3.yahoo.com and your username and your password. Apparently you did, although you didn't tell.
2. You must run that mail-program (Outlook), because it will only pull the messages out of that account when it's run. Apparently you ran the program again.

So all, you've got to do:
- change the password on the pop3-account made in Outlook; it won't be able to receive any more mail then; close the program and reopen
- forward the mail you want to keep to your yahoo or gmail-account; it will stay there
- delete the account in Outlook and close the program
- see if you happened to add Outlook to the list of programs that run automatically at boot; if so, remove it from that list
- never run the program again; if possible uninstall it
- find the .pst-file and delete that to save some disc space

Kees