[CentOS] sendmail mail relay backscatter issue.

[Les Mikesell]

On 2/4/2010 9:05 AM, Simon Billis wrote:
> > Another would be to use MimeDefang as the framework instead of
>>> mailscanner.  It has an option to check recipient addresses via smtp
>> to
>>> the delivery servers before accepting.  You may have to write a
>> snippet
>>> of perl to get that right for multiple domains (that's a feature...).
>>> This is less efficient but works in real time against the addresses
>> that
>>> will be accepted for delivery.
>>
>> I would question how "real time" that would be for every email for 6k+
>> domains. If a few have a large client base, or are expecting responses
>> from a mass emailing, it might start to take a *while*, unless you've
>> got
>> pretty heavy duty equipment and networking.
>
> I agree - I think that the overhead that perl would impose is too high for
> this application.

MimeDefang doesn't start a perl process for each operation, it 
multiplexes the milter requests from many sendmail processes to a few 
long-running perl daemons.  This is done separately for each milter 
operation so fast things don't end up waiting for slow things like the 
spam scans.  It doesn't take long for an already-running perl to send a 
few network packets to verify an address via snmp, but it does add load 
to the downstream server to do the lookup.

-- 
   Les Mikesell
    lesmikesell at gmail.com