As noted about a zillion messages ago, one of the concerns about IPv6 mail is whether DNSBLs will be workable, with one of the questions being whether the lookups will blow away DNS caches. As far as I can tell, there is basically no research on DNS cache behavior other than a few very old papers that said for normal loads, a reasonable sized cache is big enough to work. For the DNSBL stuff I'm doing some simulations, which need data to drive the lookups. The data is really simple, a sequence of pairs: [ IP address, timestamp ] IPv4 traces are currently more useful than IPv6, since v6 doesn't have the botnet traffic that makes the DNSBL lookups interesting. Traces from medium sized systems, say a million connections a day, would be great. If you consider the IP addresses confidential you can hash them, although real ones would be better so I can test tweaks that treat known high volume senders (gmail etc.) differently. Thanks. Regards, John Levine, johnl@iecc.com, Primary Perpetrator of "The Internet for Dummies", Please consider the environment before reading this e-mail. http://jl.ly PS: I hope it's OK if we take a break from reinventing patented anti-spam techniques that have failed repeatedly before to talk about something else.