OT: Sendmail REJECT or DISCARD preference

[Peter Farrow]

Richard Siddall wrote:
> Steve Freegard wrote:
>> Peter Farrow wrote:
>>> If you reject,  and its spoofed you'll get it back anyway, so you 
>>> end up receiving and then storing it in the postmaster address, it 
>>> is always best to discard in this scenario...or even worse bouncing 
>>> it again
>>
>> Huh? - explain this a bit better as it doesn't make sense to me.
>>
>
> I believe you can get in this situation if you get a lot of e-mail 
> forwarded to your servers on behalf of your clients by an intermediate 
> ISP.  If you then reject the e-mail at SMTP time the intermediate ISP 
> tries to relay the reject as a bounce and you then get backscatter.
>
> Quietly discarding the spam gets rid of the backscatter, along with 
> any false positives.
>
> Unfortunately, there's no easy way of pushing your rejection criteria 
> out to the intermediate ISPs so they can avoid accepting e-mail you 
> won't accept from them.
>
> Regards,
>
>     Richard Siddall
Precisely,
If you're running a mail server that is an intermediate scanner for 
hundreds of domains prior to final delivery at the clients servers, a 
REJECT notice that you send back which is to a false address will quite 
correctly come back to the postmaster box of the REJECT machine.  In 
this way a discard is MUCH better as you don't bother to report the 
failure to the intermediate MTA because it was junk anyway.  With a 
discard you silently bin it saving everyones time, diskspace and bandwidth.

This has to be considered in the context of a machine that scans mail 
for lots of domains for delivery to lots of clients disparate servers.  
In this context you'll find that a DISCARD is far better...