From: /dev/rob0 (rob0gmx.co.uk)
Date: Mon Oct 24 2005 - 16:52:58 CDT

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On Friday 2005-October-21 22:55, morgan wrote:
> How do I configure Postfix to receive all mail and silently discard
> invalid addresses? I am looking to thwart dictionary attacks.
>
> for instance:
snip
> 550 <invalid_address_oiwjidomain.com>: Recipient address rejected:
> User unknown in local recipient table

Looks thwarted to me.

> I'd like it to accept this address and silently discard the message.

Perhaps you are thinking that spammers take that information and prune
their lists? Years of experience seem to indicate that they do not do
this. Most spammers nowadays are using stolen resources (zombies), so
list pruning would increase costs without increasing revenue. Even the
SBL-listed spammers don't seem to do it ... I see hits from the same
ones for the same nonexistent users over and over.

Furthermore ... what harm would this pruning do to you, if it actually
was done? Fewer connections to reject: what's wrong with that? Hurt me
more! :)

> I have read all the Postfix resources I know of and I can't find the
> answer..

What you are seeking to do is in fact fairly simple. After a
permit_auth_destination restriction and whatever relaying restrictions
you may require, use a check_recipient_access with a wildcard regexp or
pcre lookup:
/^/ DISCARD
And be aware that you're now part of the spam problem, for reasons the
other posters have already given you.
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