I'm not sure what you mean by "re-directs e-mails." Are the recipient addresses changing between the time you address the message and the time it is sent? If you could provide more information I think that would help in tracking this down. When you use Firefox to work with your webmail site, whether Yahoo! or Gmail or another, the mechanics of sending the mail are handled by the site itself. So if there is a problem with how messages are addressed, then you may need to check your Yahoo! mail settings.