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Realtime Blackhole List

Short for Realtime Blackhole List, a list of IP addresses whose owners refuse to stop the proliferation of spam. The RBL usually lists server IP addresses from ISPs whose customers are responsible for the spam and from ISPs whose servers are hijacked for spam relay.

As subscribers to the RBL, ISPs and companies will know from which IP addresses to block traffic. Most traffic blocking occurs during the SMTP connection phase. The receiving end will check the RBL for the connecting IP address. If the IP address matches one on the list, then the connection gets dropped before accepting any traffic from the spammer. Some ISPs, though, will choose to blackhole (or ignore) IP packets at their routers. The goal here is to block all IP traffic.
It is important to note that all e-mail and packet blocking is done by the recipient, not the RBL administrator, which is only responsible for bouncing spam that is directed at its servers.

A great web site for checking if your server is listed in any RBL/Spam list is http://www.anti-abuse.org/multi-rbl-check/

Don't forget to add in all your servers under the relevant MTA section at least those RBLs:

Custom Sorbs dnsbl.sorbs.net http://www.sorbs.net/using.shtml
Custom barracuda b.barracudacentral.org http://barracudacentral.org/rbl
Custom spam bl.spamcannibal.org http://spamcannibal.org
System spamcop bl.spamcop.net http://spamcop.net/bl.shtml
System spamhaus zen.spamhaus.org http://www.spamhaus.org/zen/index.lasso
System spamhaus_spamcop zen.spamhaus.org, bl.spamcop.net

If you end up with serious spam issues and can't figure what to do to sort out your problem don't hesitate to contact us. We offer solutions to all spam problems while having large companies sending more than 100k emails per day without been listed as spammers (they aren't :) ).

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