|What web browser are you using? You can adjust the application settings to choose the program (sometimes even webmail) that opens up when clicking a mail link on a website.|
-In Firefox, go to Tools > Options > Applications tab > content type: mailto. Action: Use Yahoo mail. Upon clicking a mailto link now, Yahoo's email login page will load, then the Compose Mail window with the linked email address automatically appended. In the To box, remove the "mailto:" command.
Are you using the free version of Yahoo Mail or the paid Yahoo Mail Plus? Only the paid version supports email clients. Free users are limited to webmail (logging into the website).
Edit: @ Replies: The profile says Windows 7, but the post was in Windows XP.
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