On 29 Mar 2008, John Levine wrote: > to non-mail domains is significant. I have at least one host name > that was never a mail domain, but since it used to appear in usenet > headers it gets over 30,000 spams a day, every day. I'm not convinced you've identifed causality ... only correlation. I suspect that many spam sources routinely 'scan' for open port 25s and send mail .. if a connection is accepted, they assume they have a mail server. If they want a dns name for the email, they do a rdns lookup. Nothing about the assumed fallback to A or AAAA will effect that form of address lookup. Don't listen on port 25 if you don't want the mail. For your web mail, make the right headers so that a reply will work. Or arrange to have the mail depart from a valid mail server. If the recipient of your of your emails replies back, and they get a rejected message, in 15 minutes or 5 days, either way it won't be something they will know what to do with if they didn't know in the first place to not send to that address. Better to improve the basic design than to expect in 10 years when there are no IPV4 systems left that they will finally get near time notifications of a delivery failure. Or perhaps define a new ICMP message which some new revision of the mail protocol will define means to immediately return the email. It is true that most hosts don't run mail servers ... but the corollary is that the host names will be used in published email addresses so it may not matter all that much than random typos result in a missfire to an A record or AAAA record defined host. On a side note ... there is a lot of tooth knashing re. slow adoption of IPV6 ... simple fact is that EACH procedural incompatibility introduces a small issue in the minds of folks who have to manage the conversions and roll out. Will slow down adoption because of perceived increased support costs. Of course, it could end up like NAT ... ignored for purity reasons by the IETF, but used in practice... one more way the IETF margninalizes itself. Dave Morris _______________________________________________ IETF mailing list IETF@xxxxxxxx https://www.ietf.org/mailman/listinfo/ietf