A couple of days ago I moved my mail server, and inadvertently mistyped its name in the reverse DNS. After this, I noticed a message wasn't making it to the list. Investigation showed: rcpt to: nanog@nanog.org 450 Client host rejected: cannot find your hostname [83.149.65.1] info at: http://www.merit.edu/cgi-bin/mn/reversednsinfo Ok, so far so good. But when I visited the URL mentioned in the rejection message, I just got a web form saying "Please enter your e-mail address and select your organization from the list below". Obviously this is meant to do _something_, but it's entirely unclear what and why. After this the page I think should have been referred in the first place comes up: http://www.merit.edu/mn/support/reversedns.html There is also a link to a DNS checking tool. However, this tool is pretty much useless in situations such as the one in which I found myself, as it doesn't answer the real question: what is the TTL for the offending DNS information.