There is some common issues occur in the Yahoo account while forwarding Yahoo mail to Gmail then just review the settings of the Yahoo account
1. Make sure that the other Yahoo account POP server is same as the one in the Gmail account.
2. Then, Yahoo mail allows you to leave messages on the server.
3. Now, set port 110 or 995.
Yahoo Toll-Free Number
More help visit: Click Here
It looks like you're new here. If you want to get involved, click one of these buttons!