[CentOS] Recommend Mail Server

Les Mikesell lesmikesell at gmail.com
Tue Nov 24 02:14:51 UTC 2009


Christopher Chan wrote:
>    
>> By not-monolithic, I mean that now submission queuing, forwarding, and local 
>> delivery are all different processes, each running with limited credentials most 
>> of the time.  And milters also can run under different uids.
>>
>>   
> 
> All that means naught if there is a remote root exploit. sendmail 8.12.x 
> already worked like that.

How do you have a remote root exploit if you aren't running as root?

>>> Unless the supporting stuff in the milters are as efficient as 
>>> what you can get in postfix, sendmail + milters might be hard pressed to 
>>> handle some environments that postfix can.
>>>     
>> MimeDefang gets this right - it runs as a multiplexor that connects multiple 
>> processes as needed so you don't have a 1:1 ratio of mailers to backend milters 
>> and you don't have fast step waiting on slow steps to complete.  See page 31 of
>> http://www.mimedefang.org/static/mimedefang-lisa04.pdf.  Most other approaches 
>> use simple pipelines that make everything wait while spamassin runs and have to 
>> reparse the mime headers to break out attachments for each scanning step.  Some 
>> very large sites are running it.
>>

> I fail to see how that becomes an advantage for sendmail. 

It lets you control load very precisely.  You can limit sendmail to some number 
of instances that can be much larger than the number of big/slow scanning 
backend processes that you permit and the sendmails don't wait for the milters 
until/unless they need one of their functions and you don't have to start a new 
process for each message.


> I can very 
> well pair postfix and mimedefang for just spamassassin and the rest of 
> the stuff handled by native postfix features. 

Where does your virus scan go?  Since spamassassin is perl, MimeDefang can run 
it internally.

 > That at the very least
> cuts out another layer to go through for postfix. In the end, sendmail 
> is at a disadvantage having to depend on a third party for extra features.

On the contrary, having the ability to extend through external software gives 
you unlimited options.  Note that postfix eventually got around to copying this 
feature.  Also with mimedefang you can do most of your special configuration in 
perl instead of having to learn yet another syntax.

-- 
   Les Mikesell
    lesmikesell at gmail.com





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