Greetings all --
I have a QMAIL question about SMART HOSTs...
First, to clarify -- a SMART HOST is a mail server designed to be a
filter. It accepts mail for configured domains, and/or from those
domains - and then forwards them on, or blocks them, based on rules --
often SPAM filter types of rules.
Its actually pretty easy to configure QMail as a SMART HOST, just using
tcp.rules and smtproutes... but that's not my question.... but it /is
/close, so let's look at how you do that first:
_To configure QMAIL to accept inbound mail ONLY from a smart host_, you
simply create a tcp.rules entry that allows (usually unfiltered) mail
from the special server, and denies all others. You could also use
IPTables to only allow connections on port 25 from that specific host
(or hosts).
By example, assuming your smart host is at 1.2.3.4:
- In /tcp.smtp/ you might say
* 1.2.3.4:allow,RELAYCLIENT="",SENDER_NOCHECK="1"**
** :deny**
* - Or, in /iptables/, you might put
***-A INPUT -s 1.2.3.4 -m state --state NEW -m tcp -p tcp --dport 25 -j
ACCEPT**
** -A INPUT -m state --state NEW -m tcp -p tcp --dport 25 -j
REJECT**(or, I prefer to DROP, so it takes longer for the mis-configured
client to figure out there is a problem)
*
_To configure QMAIL to forward ALL outbound mail to a smart host_, you
simply make a wildcard entry in smtproutes that points all mail to that
host.
* :1.2.3.4*
This is all well and good for someone who is stuck behind their ISP's
smart host (when they block port 25 otherwise - e.g. Verizon DSL)...
BUT, what if I want to employ a SMART HOST as a subscriber SPAM FILTER
for both inbound and outbound mail -- but only for SOME domains that I
host??
Sure, I can use SPF to force inbound messages FOR a specific domain to
come from the SMART HOST (and I'm open to better ways to do that)...
But, how do I configure outbound mail FROM a specific domain to be
routed only through the SMART HOST?
- smtproutes rules apply to the receiving domain, not the sending one!
I'm interested to hear ideas....
Thanks,
Dan McAllister
QMT DNS/Mirror Admin
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