The mail to:
function always brings up an email client such as Outlook on your desktop. You can change which one it brings up by opening Internet Explorer & at the top choose Tools > Internet Options > Programs
, clicking the down arrow next to Email:
as shown in the pic below, & selecting something other than Outlook. Click Apply > Ok
& your done.
You should then configure the newly selected program to check/send your email from your ISP & your Yahoo account. If you don"t have this already installed on your computer, Thunderbird is a recommended email program to use. You can find it here: Thunderbird