OT: Sendmail REJECT or DISCARD preference

[Matt Kettler]

Peter Farrow wrote:
>>   
>  >> client is the company I am sending mail onto who use my services...
> 
> So there is *nothing* wrong with this configuration at all....
> 
> So I'll carry on doing a discard thanks,
> 

For your case, you probably should.

However, please stop misrepresenting the facts. REJECT works very well if 
properly implemented, and doesn't flood your postmaster box. However, properly 
implemented means having it on all of your MX servers, not a back-end server.

If you're filtering on a back-end server, or any other point after the DATA 
phase of the SMTP session has been OKed by a server in your network, then REJECT 
is a bad idea. At that point, a REJECT fundamentally has to result in a 
post-delivery bounce, because the message has already been delivered.

REJECT only works well if it is implemented on the server that first accepts 
mail in your network, so it can be REJECTed before original delivery is 
completed. This results in considerably better behavior by your network, and 
reduced resource utilization. REJECT should be preferred over DISCARD at your 
network borders for this reason.

DISCARD is preferable over REJECT within your network, however neither results 
in good network behavior. At this point, tag-only is probably the best behavior. 
  However, the implications are really yours to suffer, so do as you will within 
your own network.

This is really all very, very basic mail administrator knowledge.