Undelivered Mail Returned to Sender

Undelivered Mail Returned to Sender

I am getting the following 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.  

operasyon@calikiran.com.tr  Error, ERROR_CODE :550, ERROR_CODE :Rejected by dnsbl-1.uceprotect.net