> I'm not talking about DNS lookups, but about DNSBL lookups. Yes, I did interchanged them, pardon.
> You ask each dnsbl for client IP, now you will ask them for each A or MX > record. That means, number of DNSBL lookups will increase ad least two times > (for each dnsbl you already query). Hmm, I am not server administrator by profession, so maybe I do not understand it enough, but I would only add one more restriction on domain in MAIL FROM header, that would make one DNS lookup (getting IP for the domain) and one DNSBL lookup (checking that IP in Spamhaus). That are two lookups, aren't they? It is true that it is not clear whether to get A or MX records for the domain. For my example the blacklisted IP address is within A record. I guess there is usually only one A record for each domain? > Note that some dnsbls require (payed) subscription if you use them too much. This is my first mail server so I need to check which restrictions work best. Then I will optimize number and order of restrictions. > we aren't talking about domains, but IP addresses of servers the domains > point to, correct? I think Allen spoke about domains. So did I. It is probably true that building blacklist of IP addresses would be better idea than building list of domains. Because I guess spammers have more domains than IP addresses…
