Jarod C. Wilson wrote:
> Steve Cowles wrote:
>> Robert L Cochran wrote:
>>> Just by way of commentary -- I'll have to find a backup mail
>>> server some day -- perhaps with a friend living far away who
>>> keeps a machine on 24X7. I wonder how many businesses and
>>> individuals went without backup mail service when the power
>>> went out in New York.
>>
>> Just my two cents on this...
>>
>> Unless overidden, most MTA's default configurations will try to
>> deliver e-mail for 5 days. So configuring a backup MX for your
>> domain will not necessarily help until after the fifth day of outage.
>
> You are incorrect. Having a backup MX will help immediately.
> In the case where your primary MX is down, the sender's MTA will
> try your secondary MX pretty much right away. MTA's will try to
> deliver the message to each of the listed MX's, in order of their
> priorities, and the 5-day wait doesn't come into play until all
> possible MX's have been tried. All sensible MTA's work that way;
> they don't wait 5 days before trying a secondary.
>
> Also, keep in mind that the primary MX isn't necessarily always the
> final destination for the email...
You're right! I should have clarified my reply with something like "Once the
backup MX has accepted (and queued) the e-mail due to the primary MX (the
final destination) being down".
The five days I was referring to is from the sendmail default. (e.g. from
the sendmail README)
confTO_QUEUERETURN Timeout.queuereturn
[5d] The timeout before a message is
returned as undeliverable.
Steve Cowles
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