Re: [courier-users] Re: Automatically use secondary MX host if primary

Malcolm Weir wrote:

>>-----Original Message-----
>>From: Sam Varshavchik
>>Sent: Tuesday, June 21, 2005 12:11 PM
>>
>>
>
>
>
>>>>So, until modern technology advances to such a point, the
>>>>only logical
>>>>thing to do is attempt to deliver E-mail repeatedly, and follow the
>>>>preferred logic for making each delivery attempt: pick a
>>>>primary MX at
>>>>random, if you can't connect it to it, pick a secondary MX
>>>>at random, and so on.
>>>>
>>>>
>
>
>
>>>I have to admit I am starting to come around to understanding
>>>Rodrigo's viewpoint on this, however. What is the *downside* of
>>>having Courier retry a different (same-priority if exists, or next
>>>lowest, as usual) MX rather than the same
>>>*potentially*-broken one, after the usual interval?
>>>
>>>
>
>
>
>>If there are multiple primary MXs set, Courier should already
>>pick one at random with each delivery attempt.
>>
>>
>
>And, contrary to the implication, it would be a BAD idea to include logic
>that selects lower priority ("secondary") MXs for the subsequent attempts
>unless (all) the higher priority ones cannot be contacted.
>
>Why?
>
>Well, how do you know that the _list_ of MXs hasn't been changed between
>attempts?
>
If this is a concern, Courier can fetch a new list at every delivery
attempt. Discard the ones it already tried and pick the remaining top
priority one.

> And if it has, presumably the recipient had a reason for so
>doing.
>
>
I agree.

>Multiple MXs with priorities are largely an artifact of unreliable
>multi-path networks (i.e. dial-ups).
>
I'm really in no position as to speak about the reasons other sys admins
might setup multiple MXs with priorities. The real fact is that they
still do. I'm just trying to make the best use of it.

> In this day and age, the chances of
>usefully using secondary MXs seems to me to be slight, except in a few
>specialized cases.
>
Well, maybe I'm just a lucky guy but I have to regulary send messages to
two different domains with different misconfigurations for which such a
feature would be very helpfull.


Rodrigo



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