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What RBL's, if any, do you use if we may ask?

I currently use:

sbl-xbl.spamhaus.org dnsbl.ahbl.org list.dsbl.org dnsbl.sorbs.net bl.spamcop.net dnsbl.njabl.org spews.dnsbl.sorbs.net cbl.abuseat.org relays.ordb.org

Just FYI, it's my understanding that the cbl.abuseat.org list is included in the sbl-xbl.spamhaus.org list so you can save yourself the DNS query. Also, the use of spamcop should (in my opinion) be suggested with a caveat that the user read up on their own description of their criteria for blocking mail. I have seen large email providers and even ISPs etc blocked by this list, even if temporarily.

Just my 2 cents,

Alex