On Wed, 17 Sep 2003, Dean Anderson wrote: > Your mail client was making a false assumption. That is a bug in the > software. The mail client shouldn't be looking up domains. It should be > sending it to the relay. The relay then decides where to send the message. > The relay may be configured to route non-DNS domains, or do translations > to other systems. Your mail client can't know about that. If the relay > can't send the message somewhere, then it is supposed to bounce the > message. This decision is made by the relay, not the mail client. > > Your mail client has had a bug, for a long time. Its not a bug. As many pointed out RFCs specify that mail servers should attempt to get MX record for domain first but if it fails should use "A" record if it exists. This behavior has existed for long time, but I think it came from way early on the internet when MXs were not used by everybody and mail was still being routed directly to the machine specified. Its possible that this is also used (dont know how much) for internal mail routing (i.e. when email@companydomain.com is received by public mail gateway it is then rerouted to your.name@corporate.mailserver.domain.com and mail administrator is too lazy to enter MX for corporate.mailserver possibly because they are not even using DNS internally and are using WINS or domain is directly in the mail routing gateway, like in /etc/hosts) What would be interesting is too try to get some statistics on how much the direct A DNS records (as opposed to MXs) are really used nowdays and if the number if sufficiently small (on the public internet, i.e. if its done on company net as described above, then mail routing software may handle case as it wants anyway), it maybe good idea for IETF to release update BCP to specify that mail should ALWAYS be routed to MX record and failure maybe issued if it does not exist. -- William Leibzon Elan Networks william@elan.net