EMAIL ACCOUNT HIGHJACKED

EMAIL ACCOUNT HIGHJACKED

In the past hour someone has tried to send over 150 emails from my account and I recieved this type of response below. The email is flooding my inbox and I have NO idea why this is happening?????

Message from yahoo.co.kr. Unable to deliver message to the following address(es).

  < chadol03@yahoo.co.kr>:This user doesn't have a yahoo.co.kr account ( chadol03@yahoo.co.kr) [0]

  < dkxns@yahoo.co.kr>:

This user doesn't have a yahoo.co.kr account (dkxns@yahoo.co.kr) [-5]

  < dnjsdudwn777@yahoo.co.kr>:

This user doesn't have a yahoo.co.kr account (dnjsdudwn777@yahoo.co.kr) [-5]

  < ini05184@yahoo.co.kr>:

This user doesn't have a yahoo.co.kr account (ini05184@yahoo.co.kr) [0]

 

<kimsangg@yahoo.co.kr>:

This user doesn't have a yahoo.co.kr account (kimsangg@yahoo.co.kr) [-5]

  < qhdrbtjsgml2000@yahoo.co.kr>:

Sorry your message to qhdrbtjsgml2000@yahoo.co.kr cannot be delivered. This account has been disabled or discontinued [#102].

  < speedzon@yahoo.co.kr>:

This user doesn't have a yahoo.co.kr account (speedzon@yahoo.co.kr) [0]