RBLs and RHSBLs work differently. RBLs list the IP addresses of machines, RHSBLs list the domain names.
Advantages of RBLs: they can list IP addresses of machines without rDNS names, they can list whole blocks of IP addresses that may host many different domain names, a listed IP address will remain blocked even if the domain name changes, they can be checked very quickly when the remote server first connects. Disadvantages of RBLs: spammers tend to move their servers a lot so RBL listings can quickly become outdated, one IP address can host many domains and blocking them all may not be fair. Advantages of RHSBLs: all listed domains are blocked no matter what IP addresses they use, the sender's email domain name can be checked in addition to the server's IP address. Disadvantages of RHSBLs: more network activity is required before the RHSBL can be checked, spammers tend to change their domain names a lot so RHSBL listings can quickly become outdated. Disadvantage of both: when using a list maintained by someone else, your mail is at the mercy of their policies. Blacklists are not silver bullets. Every list operator has different rules for being listed and delisted. Some are more lenient than others. For example, some operators require a server to send multiple spams to a honeypot address before they will be listed. Others require only one. Some operators will delist anyone who asks (and relist them if they re-offend). Others require lengthy processes, including monetary payment. Before you use a list, you should read their policies very carefully and do some basic searches for complaints against them (not all operators follow their written policies). Blacklist operators have been known to list huge blocks of IP addresses in attempts to pressure ISPs to cancel spammers' accounts. You must be sure you are willing to be part of those actions. In other words, the list operator is only responsible for the list. You are responsible for your mail server. As to the risk of false positives, every filter can incorrectly reject legitimate email. Every administrator must experiment to determine how many rejections they are comfortable with. Personally, on my server, I use all four of the filters you mentioned (and more). For me, the most problematic is "reject-unresolvable-rdns" but I'm willing to whitelist the few legitimate senders that are incorrectly blocked. I feel the benefit outweighs the inconvenience; that's my decision to make. -- Sam Clippinger Paolo wrote: > Hello everybody, > > I hope this is not a FAQ , I'd like to know if there is some reason to > prefer rbl to rhsbl . > > Wouldn't it be nice to write down a list of options with explained how > much is the risk of rejecting good mail ? > > for example in my configuration I've not enabled these options and would > like to know if they could generate many false positive: > > reject-empty-rdns > reject-missing-sender-mx > reject-unresolvable-rdns > reject-ip-in-cc-rdns > > > Maybe it could be useful to make a survey of people's enabled options > and most used rbl ? > > Thank you > Ciao > Paolo > > > ------------------------------------------------------------------------ > > _______________________________________________ > spamdyke-users mailing list > [email protected] > http://www.spamdyke.org/mailman/listinfo/spamdyke-users _______________________________________________ spamdyke-users mailing list [email protected] http://www.spamdyke.org/mailman/listinfo/spamdyke-users
