I have a Yahoo Mail Plus Account and have tried to have it forward to my Outlook.com account.  I have tried to have it do so with a "send only" account as well as a "send and receive" account.  In Outlook.com when I try to set up with the "send and receive" account it says I need to have Yahoo Plus.  I have had Yahoo Plus for a long time, and it always comes up with this message, and will not complete the forwarding.  I do not receive that message for a "send only" account, however, the "send only" doesn't forward my E-Mails from Yahoo so it is useless. 

In many of the responses on this topic you have private E-Mail communications.  No problem with me except that it doesn't provide a solution for users like myself.  Can you please help me and perhaps others on this forum with this problem.  It seems to be a common issue, that has yet to be resolved.