From: Barbara M. (barbararfx.it)
Date: Wed Mar 12 2008 - 08:28:58 CDT

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This is the situation:

Internet
    |
    |
    | (a.b.c.d)
    FW
    | (192.168.1.1)
    |
    |
   SWITCH (DMZ)
    |
    |
    |-SMTP-IN (192.168.1.2) (Postfix 2.1.x, spamassassin, clamav, sqlgrey)
    |
    |-MAIL (192.168.1.3) (Postfix 2.1.x, dovecot, procmail)
    |
    |-SMTP-OUT (192.168.1.4) (Postfix 2.1.x, spamassassin, clamav)

Some hundred domains; Mails come in via the public IP a.b.c.d that is
forwarded to the internal box SMTP-IN where if they pass sqlgrey are
scanned for virus/spam and forwarded to MAIL (only header are modified).
Outgoing mail go via SMTP-OUT.

All ok until some weeks ago when we start having daily mail stats like
this:

   Postfix log summaries for Mar 10

   Grand Totals
   ------------
   messages

   58803 received
   59638 delivered
       2 forwarded
     773 deferred (5920 deferrals)
    5813 bounced
    1396k rejected (95%)
       0 reject warnings
       0 held
       0 discarded (0%)

    5327m bytes received
    5797m bytes delivered
    9682 senders
    7670 sending hosts/domains
    6292 recipients
    2025 recipient hosts/domains

We have over 1 million mails/day. :-( 95% rejected from greylisting.
Logs grow very rapidly ... :-(

I think a good idea can be using RBL (disabled in the past because they
create various problems).

Our needs are:
- some hints for using RBL "safely" (great chances of experiments in
production box).
- hints/links/config-examples to build new box that replace our SMTP-IN

Regards, B.

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