Undelivered Mail Returned to Sender

Undelivered Mail Returned to Sender

 INVALID_ADDRESS, ERROR_CODE :554, ERROR_CODE :5.7.1 Service unavailable; Client host [135.84.80.217] blocked using dnsbl.sorbs.net; Currently Sending Spam See: http://www.sorbs.net/lookup.shtml?135.84.80.217

This is what I get. I am blocked now. Could you please solbe the issue asap?