John C Klensin wrote: > I've got two separate and unrelated incidents in the last 10 > days in which RBL lists have decided to block some (but not all) > of Comcast's outbound mail servers. Interestingly, this draft is about both blacklists and whitelists. Many large domains maintain whitelists of other large mail domains. For example, our comcast.net outbound servers are all listed here at http://postmaster.comcast.net/outbound-mail-servers.aspx and you can get an RSS feed of the addresses so that you can get updates. But every large sender tends to do this in an entirely different way. And, here is how we list our dynamic IP address space, at http://postmaster.comcast.net/dynamic-IP-ranges.aspx and in RSS feed at http://postmaster.comcast.net/dynamic-ip-ranges.xml. In the case of dynamic space, several DNSxBLs exist that aggregate ISP dynamic IP space to make it easier on large domains to put all of those together. Jason _______________________________________________ Ietf@xxxxxxxx https://www.ietf.org/mailman/listinfo/ietf