Re: Filtering inbound e-mail via aliases, BEFORE Maia handles

> Actually, rejecting those messages consumes far less
resources than
any of the other 
> options. It's even quicker than silently discarding it,
and orders of
magnitude faster than 
> feeding it blindly to your poor overloaded mailguard
server.

> Once you accept the message for a nonexistent user, you
have to go
through all the work of 
> bouncing it. Far better to simply reject it at the smtp
threshold and
be done with it.

> > >I use Postfix, and there are many was to
accomplish this:
> > 
> > But but but... it's not sendmail! ;)

> No, it's a drop-in replacment for sendmail which is
faster, more
secure, and consumes less 
> system resources. Works for me!

I'm continually pleasantly surprised by postfix... This post
led me to
'Recipient address verification'

http://www.postfix.org/ADDRESS_VERIFICATION_REA
DME.html#recipient

Turned it on - and removed the whole management of
valid/invalid
recipients and backscatter in an instant - it
*automatically* builds and
maintains a list of valid users on the downstream servers
and rejects
any invalid users on receipt - before maia/amavisd has to
churn through
them...

CPU load on the server has halved instantly... And queue
times have
plummeted.

Now I've just got to get my worst end-users to turn off
catchalls!!

-Craig
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> I'm continually pleasantly surprised by postfix... This
post led me to
> 'Recipient address verification'
>
> http://www.postfix.org/ADDRESS_VERIFICATION_REA
DME.html#recipient
>
> Turned it on - and removed the whole management of
valid/invalid
> recipients and backscatter in an instant - it
*automatically* builds and
> maintains a list of valid users on the downstream
servers and rejects
> any invalid users on receipt - before maia/amavisd has
to churn through
> them...
>
> CPU load on the server has halved instantly... And
queue times have
> plummeted.
>
> Now I've just got to get my worst end-users to turn off
catchalls!!

Craig,

If you haven't already, look into these two main.cf
parameters that relate
to Recipient Verification.

address_verify_map = btree:/var/spool/postfix/verify
unverified_recipient_reject_code = 550

The first one will build a local cache of results and keep
those for 30
days.  This helps reduce the number of downstream lookups
for mail
received for the same bogus recipients.  The second tells
Postfix to 550
the messages (permanent failure) instead of 450 (temporary
failure) which
is what Postfix does by default in the absence of this
setting.

The catch-alls will make this feature useless, so if you can
encourage
disabling that, you should see a noticeable increase in smtp
rejections.

Ryan


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