Normally if you have such an error:
553 your ip is currently blacklisted, try to auth first (XXX.XXX.XXX.XXX.sbl-xbl.spamhaus.org)
It means that the IP you are connecting from your ISP is in the blacklist of Spamhaus, you may want to contact your ISP to have it removed. Alternatively if you are using a dynamic ADSL connection, try to off and on the routers/modems and try again. Doing that should assign a new IP for you.