Julian Mehnle <[EMAIL PROTECTED]> wrote: > Don't get me wrong: I don't really see a harm in accepting > MX->IP *in general* (although there still might be one which I > don't see).
After having thought about the topic a bit and having consulted RFC 1035, I think there *is* a serious argument against accepting MX->IP: RFC 1035 (DNS), section 3.3.9 says that an MX record specifies a domain name, not an IP address. This distinction is important since the DNS protocol stores IP addresses in a way much different from domain names (raw address bytes vs. compressed variable-length series of labels). Now think of IPv6 addresses and AAAA or A6 records. In the next few years, most hosts will get an IPv6 address next to an old-style IPv4 address. For an MX, this will be correctly represented in DNS as follows: mydomain.com. MX 10 mail mail.mydomain.com. A 12.34.56.78 mail.mydomain.com. AAAA 1234:5678::1 It just makes no sense to directly specify a single IP address in an MX record for any host accessible through multiple protocols/interfaces. Which address would you put into the MX RR? Not even talking about creating multiple MX RRs for multiple addresses of the same host (mydomain.com. MX 10 12.34.56.78; mydomain.com. MX 10 1234:5678::1), which would be a gross abuse of DNS. Aiding such abuse is no good. DNS masters should just do their homework themselves, instead of expecting authors of DNS resolvers (or mail server software) to do it for them. ------------------------------------------------------- This sf.net email is sponsored by:ThinkGeek Welcome to geek heaven. http://thinkgeek.com/sf _______________________________________________ courier-users mailing list [EMAIL PROTECTED] Unsubscribe: https://lists.sourceforge.net/lists/listinfo/courier-users
