If you're having difficulty receiving mail forwarded from your Yahoo Mail account, there are a few things you should check.
- Ensure that you've entered the correct address in the "Forward your Yahoo Mail" box. Click Options in the upper-right corner of the Mail page and select More Options. From the list on the left, click POP & Forwarding. Examine the address in the Forwarding section. Is it the right one, with no mistakes in it?
- Check that you haven't set up any filters in the external account/email client that might be sending messages to other folders.
- Ensure the account you're forwarding your Yahoo Mail to hasn't exceeded its storage quota. If the email account you are forwarding to is exceeding its quota, this might cause messages sent to that address to be returned. If you're over your quota, you'll need to delete mail until you're again able to receive messages. To be safe, you'll probably wish to leave at least 1MB of free space in that account.