It does happen that the users are complaining that the mail they are sending is not getting delivered to the recipient’s mail box. Before complaining you must check whether you have typed the mail address appropriately. If not then retype the email address correctly and send the mail. If this doesn’t help then ask the recipient to contact their service provider as there might be some Issues In their internal servers, as the mail Is not getting downloaded. This should resolve the Issue, or else you can call the yahoo help number at any point of time. They will be more than happy to help you.