IP has been found on a block list

IP has been found on a block list

Hello,

I'm having troubles sending e-mails to an address. Here's the error message I receive:

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.

INVALID_ADDRESS, ERROR_CODE :550, ERROR_CODE :5.7.1 Recipient not authorized, your IP has been found on a block list

I sent an email a couple of days ago to this e-mail address and everything was fine.