Philip Hazel wrote:

> On Tue, 17 Oct 2006, Rene Marticke wrote:
> 
> 
>>let me explain two scene why this callouts are abuse.
>>
>>1.
>>[EMAIL PROTECTED] send mail to [EMAIL PROTECTED]
>>--> domB callout whith [EMAIL PROTECTED] if [EMAIL PROTECTED] is valid.
>>--> domA use callout to -> so call domB if [EMAIL PROTECTED] is a valid 
>>user .... loop
> 
> 
> That is precisely why Exim does *not* do a callout with [EMAIL PROTECTED] 
> to verify a sender. It does the callout with "<>" as the sender. We've 
> had this discussion several times. There are some options for varying 
> the callout sender for recipient verifications (when one is generally 
> talking to another of your own MTAs), but not for sender verifications.
> 

ACK. Exim is polite and 'careful'. Most other 'major' MTA are as well.

- But even if all were such, spammers/zombies have poisoned the well, making 
mailadmins ever more paranoid. Chances of blacklisting aside, fewer and fewer 
servers give useful responses.

A defensive 'delay' vs typical callout timeout alone means I may even defeat 
such checks between my *own* servers!  Else need more patience than is 
warranted 
for the  already dodgy results...

Never-ending battle, it is.

:-(

Bill




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