Yahoo Mail is one of the world's leading email service providers. With increasing numbers of malware attacks which are spread over the internet via email attachments, Yahoo Mail had introduced Norton as the resident antivirus programme on its email servers which scans any attachments that are downloaded by users. This can sometimes cause errors for users who have another antivirus on their local systems which is scanning the email attachments as well. In case of such a conflict, where two antivirus programmes are running at the same time, the user may not be able to download the attachment.
I'm unable to download any attachments from my Yahoo emails. The statement "The requested URL was not found on this Server" always pops up.
This problem is because of your antivirus software. If you're using Trend Micro, go to Virus Controls; then Protection Against Viruses; click on Settings and untick the box next to "Threats in Web mail attachments". Remember, Yahoo uses Norton to download attachments and you can't have two virus protections "running" at the same time.
Thanks to https://ccm.net/forum/affich-33677-can-t-download-attachments-on-my-yahoo-email
for this tip.