[CentOS] Recommend Mail Server

Christopher Chan christopher.chan at bradbury.edu.hk
Tue Nov 24 08:03:30 UTC 2009

Les Mikesell wrote:
> Christopher Chan wrote:
>>> 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?
> Yes, but it is pretty unlikely that the results will be different since they are 
> both done quickly against the authoritative source.  Unlike if you had made an 
> intermediate copy of the database.

You can chain lookups. At least in postfix. So the results will be the 
same if you had a local copy in cdb format.

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