Paul Vixie vixie at
Mon Feb 22 13:34:43 CST 2010

John Levine <johnl at> writes:

> I now do nearly all of my spam filtering during the SMTP session.


> There might once have been a reason to accept quickly and chew through
> the mail later, but these days it all needs chewing so you might as
> well do it right away.  This has the huge advantage that you can
> reject unwanted mail after data with 550 FOAD rather than bouncing.

there was once an argument for silent discard on spam, to keep spammers
from being able to tune their entropy to get past one's filters.  these
days the spammers don't have to tune anything and don't tune anything,
so there's no advantage to silent discard or to asynchronous filtering.
everything that can be rejected synchronously, should be.  there's a
small chance that the rejection notice will go to a nonbot nonspammer
who can correct their mistake and retry.  that chance is worth taking.
Paul Vixie

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