since yahoo mail is web mail it isn't as simple as changing from dedicated email clients such as Outlook to Thunderbird or vice versa - it requires a third party intervention.
Here is a link that should help - it REQUIRES installing the yahoo toolbar. This assumes that your default web browser is Internet Explorer and NOT firefox.
Alternatively you can follow these instructions and set Yahoo mail as the default in both firefox and MSIE --
PC -- Internet Explorer or Firefox
1. From the ?Start? pop-up menu in the lower left corner of your desktop, select ?Settings? then ?Control Panel?.
2. In the Control Panel, select ?Internet Options?. This opens the ?Internet Properties? window.
3. Click the ?Programs? tab along the top.
4. Click the ?E-mail? pull-down menu, and select Yahoo! Mail*
*Are you not seeing Yahoo! Mail in your list of E-mail programs? Download Yahoo! Messenger. It?s easy, it?s quick, and it puts Yahoo! Mail in your E-mail application list.
I have a Dell Inspiron i545 desktop with an Intel Core 2 quad processor and 8GB of memory which is running Windows 7. Many times when I want to email a web page I have found to another person, it wants me to use WINDOWS LIVE as the email (I only use Yahoo and don't even understand how to set up Windows Live ... sorry!) Anyway, I followed the instructions to make Yahoo Mail my default but when I follow them, it is not a choice.
Can anyone give me a simple explanation of what I can do? I really appreciate everyone's help and learn a lot here. Also at times, I see requests for SMTP & POP3 addresses (I use Comcast high speed internet connection) and don't know what they are. Yes ... there are some of us old timers out here who can be frustrated by even the most mundane things ... but I'm trying!
Thanks to all.
pls lmk if I haven't given enough technical information in order to be helped.