----- Original Message -----
From: <francisvdagupan.com>
To: <postfix-userspostfix.org>
Sent: Thursday, November 21, 2002 2:16 AM
Subject: Recommended RBL setting

> Hi,
>
> What are the pros and cons of having more than 3 maps_rbl_domains?
Example:
>
> maps_rbl_domains =
> blackholes.wirehub.net
> dynablock.wirehub.net
> dnsbl.njabl.org
> relays.ordb.org
> relays.osirusoft.com
> proxies.relays.monkeys.org
> opm.blitzed.org
> sbl.spamhaus.org
>
> Will Postfix query each and every host listed?
>
> ---
> francis a. vidal [bitstop network services] | http://www.bitstop.ph
> streaming media + web hosting | http://www.keystone.ph
> v(02)330-2871,(02)330-2872; f(02)330-2873 | http://www.kuro.ph
>

Postfix will check as many RBLs as you care to list. They are checked
in the order you list them.

pros: each RBL has individual listing criteria, they are not just
duplicates of each other. Some spam sites will only appear in some
RBLs. You will likely block more spam this way.

cons: more DNS lookups (whether this is a problem depends on your mail
load).
More false positives. Each list has SOME false positives, the more
lists you use, the more false positives you expose yourself to.
Some RBLs are very aggressive, and some have rather harsh - or no -
removal policies.

What is right for YOU depends greatly on what kind of mail you receive,
how many users you are responsible for, and what your tolerance is for
rejecting good mail by mistake. An RBL set used for a home or small
business machine is very likely not suitable for an ISP, and vice versa.

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