Email ???

[Les Mikesell]

Steve Friedman wrote:

>> How does it work?  If it pauses the current connection with that server,
>> independently of any other system trying to send you mail, then only one
>> thing at a time gets delayed, so it shouldn't be a DOS.  But if sendmail
>> pauses completely while one thing talks to it, and won't do anything
>> else until that task is completed, yes, I see potential problems.
>>
> 
> It's a DoS because the system can have only a finite number of sockets 
> open (this is both a kernel limit and a postfix tuning parameter limit), 
> and greet pause ties them up doing nothing for a period of time.  Recall 
> that postfix is written to support many operating systems and not all 
> OSs (especially the older ones, e.g., linux 2.4) support epoll (enabling 
> greater than 1024 elements in the select()).  Consequently, on an active 
> server, legitimate connections will be denied because of a lack of an 
> available socket and thus you've denied service to a legit user.

Good luck at explaining that to rabid anti-spam fanatics who don't care 
how much damage they cause others in their quest to avoid having to hit 
the delete key.

-- 
   Les Mikesell
     lesmikesell at gmail.com