> Matus UHLAR - fantomas writes:
>
>> I'm aware of this. Unluckily, some of our customers tend to make many
>> mistakes so the mail bounce (and they quite often misconfigure their source
>> address so the mail double-bounces).
>>
>> Therefore I would like to push the checks at smtp time.
>>
>> Currently courier does:
>> - validate sender domain
>> - validate recipient address, if it's local.
>>
>> What would I like to add:
>> - validate recipient domain
>> - validate sender address
>>
>> And I'd like to change address validation that it would be validated, if
>> it's known, not only if it's local.
>>
>> This could give us advantage on MX relays, which could e.g. mirror
>> recipients database using ldap...

On 26.05.10 07:01, Sam Varshavchik wrote:
> All of this incurs non-trivial per message overhead. Issuing a DNS query, 
> and/or querying the local account database, is not free, and the penalty  
> now applies to every message. A judgement call needs to be made whether 
> the additional overhead is justified by the value added.

I'm aware of all of this. However all (except sender address verification)
the overhead will still happen, but later in delivery chain, in which case
it's much harder to tell sender what was the problem with the message, and
even if, the overhead in such case is much bigger.

I'm willing and able to accept a little more overhead during the SMTP
transaction, because in many cases it will result in much less overhead
during later phases of delivery. And you can believe me, having bunch of
undeliverable mail in queue causes much more troubles to us than issuing
some DNS lookups (1 per recipient, but quite cheap) and database lookups (a
bit more expensive, but only one per sender, e.g. mail).

> As the old saying goes: build an idiot-proof process, and nature will 
> evolve a better idiot.

Do you mean we shouldn't build idiot-proof processes because of this?

-- 
Matus UHLAR - fantomas, [email protected] ; http://www.fantomas.sk/
Warning: I wish NOT to receive e-mail advertising to this address.
Varovanie: na tuto adresu chcem NEDOSTAVAT akukolvek reklamnu postu.
Chernobyl was an Windows 95 beta test site.

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