[CentOS] Recommend Mail Server

Christopher Chan christopher.chan at bradbury.edu.hk
Tue Nov 24 06:47:28 UTC 2009


Les Mikesell wrote:
> Christopher Chan wrote:
>   
>>     
>>     
>>> If you have a reasonably fast internal mailer you can just let mimedefang on 
>>> your external relay check against it with smtp in real time.  Exchange isn't one 
>>> of those, though.
>>>
>>>   
>>>       
>> That internal mailer still has to whack something. You would just be 
>> adding another layer again with the smtp latency. What is with the love 
>> of uber number of layers?
>>     
>
> You are removing a layer if you just pass through the recipient check to the 
> ultimate source (the internal delivery machine) before accepting, and it does in 
> fact need to be able to handle the lookups at the speed real messages come in. 
> However, your external relay is likely to get whacked with a dictionary attack 
> that it needs to be able to reject quickly so you can't do that if the delivery 
> box is slow.
>   

OH are we? So what happens when the frontend hands off to the internal 
delivery machine? Does not the internal delivery machine again do 
another lookup?

> I used qmail for one of my domains a while back and it's practice of accepting 
> everything, then sending bounces got a dictionary attack onto some kind of 'good 
> to spam' list and I got about 50,000 messages/day for non-existing users for 
> years afterwards.  That was a problem until I put a sendmail with the good users 
> in a virtuser table in front of it.  Interestingly, the messages would come in 
> from a large number of different IP addresses but in a sorted order and with 
> clearly coordinated timing.
>
>   


/me shudders to think of anyone running a pure qmail-1.03 for a mx.


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