> That is all well and good, but it is completely of value to the receiving > MTA, and under their complete control. There is nothing that requires a > receiving MTA to follow this model, despite what others may see as value. well, if you want to receive mail from other domains without special arrangement, you need to specify in DNS how those other domains should send mail to you. and you do that by following the instructions in the mail standards, rfc2821[bis] in particular. if you don't want to receive mail from other domains, or if you're willing to make special arrangements with the domains from which you wish to receive mail, you have no particular requirement to follow the specifications for how to advertise this in DNS. but hey, if you're willing to work out your own way of doing something, you don't need standards. that's not what standards are for. > I agree that if an MX exists, the operator of the receiving MTA has stated > its expectations, and the sending MTA needs to oblige. That is not the same > as mandating that every organization has to follow the same model. again, they only need to follow that model if they want to receive mail without making special arrangements with the sender. if they want to do arbitrary things, like use a different mail transfer protocol or a different port or a different way of advertising things in DNS than the standards say, they're welcome to do so - but they shouldn't expect to receive mail. > If there were some serious technical consequence for lack of the MX record I would be > all for specifying its use. Operational practice with A records shows that > there is no real issue, only if you ignore the problems that have been observed and the increased likelihood of such problems occurring in IPv6. Keith _______________________________________________ IETF mailing list IETF@xxxxxxxx https://www.ietf.org/mailman/listinfo/ietf