OT: Sendmail REJECT or DISCARD preference

[Steve Freegard]

Steve Campbell wrote:
> Since we're hitting the access file pretty hard today, I thought I'd ask 
> a question about what most might put in there.
> 
> I typically use the DISCARD parameter instead of the REJECT, with the 
> reason being I don't want to add to the trash on the web. What do most 
> use here and am I correct in thinking that DISCARD is less bandwidth and 
> CPU intensive?

Nope - 100% wrong in my opinion.

If you use DISCARD, then you take the message all the way to the end, 
pretend to accept it and then /dev/null it.

There are two really important disadvantages:

1)  Throwing messages into the bit-bucket is really dangerous as if you 
get an FP here (say through a mistake in the LHS of the access-map) then 
you'll never know and neither will the server without some debugging.

2)  You'll use extra bandwidth as DISCARD will take all of the message 
data, then throw it away.

REJECT is better because:

1)  It is done pre-DATA, so therefore potentially saves a lot of bandwidth.

2)  As per the RFC - the sending MTA has to deal with the rejection, 
this means for a FP the sending MTA that receives the rejection must 
generate a DSN to the originating user.

Hope this helps.

Kind regards,
Steve.