On 24 Jun 2005 at 10:42, Rodrigo Severo wrote:

You're right. I didn't 'tune in' until DNS entered the discussion. I watched the thread for a while, but didn't go back to read earlier messages.

Thanks for reiterating the issue for lazy readers like me.

I can see the problem. On the other hand, a list of MX records of the same priority actually advertises that you don't care which one the sender chooses. It's all the same to you. Implicit in that statement is the promise that they will all act the same if they respond at all. If one of them is broken and providing a different response than the others, the presumption is that it's the responsibility of the receiving admin to remove it from the list of available systems. What you're proposing really seems to me like a subtle alteration in the meaning of an MX record. It's not truly, 'Pick any of these of the same priority. I don't care.' It becomes, 'I want attempts distributed among them all so an error on one (that leaves it responsive, but returning a temporary error) doesn't stop mail delivery.' A broken system is a broken system and needs to be taken offline until fixed. What if it broke and was returning a permanent error? Then retries wouldn't even enter the picture.

So even though I understand the issue being raised now, I still don't really agree it's appropriate to attach more meaning to an MX record. If Sam comes up with a slick, cool way to randomize an MX list without impacting performance at all I don't have any strong objection. But I do see it attaching more meaning to the MX record. Now you do care which one you pick. Caring that it's random or that it is tries them all (other than when one or more is unresponsive) is still caring.

Scott