ERROR CODE :550 - The sending IP is listed on https://spamrl.com as a source of spam.

ERROR CODE :550 - The sending IP is listed on https://spamrl.com as a source of spam.

How to avoid this type of error?

"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.

 ERROR CODE :550 - The sending IP is listed on https://spamrl.com as a source of spam."