Hi,

I was trying to send a mail but this mail delivery 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. 

foo@bar.com Invalid Address, ERROR_CODE :554, ERROR_CODE :5.7.1 Service unavailable; Client host [72.5.230.103] blocked using zen.spamhaus.org; http://www.spamhaus.org/query/bl?ip=72.5.230.103