550 error message undeliverable

550 error message undeliverable

I've received this undeliverable error message on certain emails recently:

This message was created automatically by mail delivery software. ....A message that you sent could not be delivered to one or more of its recipients. This is a permanent error....
(email of person I was contacting).... Error, ERROR_CODE :550, ERROR_CODE :SC-004 (COL004-MC4F15)

It also says:
The problem is that too many unwanted messages have been sent from the following IP address above.You can also refer your provider to http://mail.live.com/mail/troubleshooting.aspx#errors .

I'm confused by this. Is the problem on Zoho's end, my computer, or the email software of the person I'm contacting? If it's on my end, how do I resolve it.