My mail (Capitan) was being autoforwarded to Yahoo. Yahoo took 2 years to let us know that user accounts had been hacked, so that was the last straw. I cancelled my account, but I can't stop one of my computers from trying to forward to Yahoo. People are getting notices that the mail is not going through to Yahoo. I have looked and looked, but I can't crack the code.
How did you set up forwarding? On the e-mail server, a rule......? What e-mail account was being auto forwarded? More information would help.