Re: Configuring DSPAM as front-end MX relay with postfix

Tom Hendrikx <[email protected]> Tue, 10 Jun 2014 23:55:04 +0200
Newsgroups	gmane.mail.spam.dspam.user
Message-ID	<[email protected]>
Hi,

I think the regular postfix integration docs should help you out:
http://sourceforge.net/p/dspam/code/ci/master/tree/doc/postfix.txt

This doesn't do before-queue like Reindl suggested though. While that's
better from an anti-spam perspective, dspam doesn't support that out of
the box. For true pre-queue filtering with dspam, you need additional
tooling, such as https://github.com/whyscream/dspam-milter (and
http://www.postfix.org/MILTER_README.html).

Regards,
	Tom

PS: I just noticed that the main README suggests that dspam can run as a
postfix smtpd proxy, but it points to the doc/relay.txt document that
clearly describes an alternative way to setup dspam as an after-queue
filter. Sorry about that :)


On 06/09/2014 01:13 PM, ML mail wrote:
> Bad news here, I just tried integrating dspam in postfix's before
> queue filtering and it only accepts the SMTP protocol whereas dspam
> server/daemon uses only the LMTP protocol:
> 
> postfix/smtpd[4131]: warning: proxy unix:/run/dspam.sock rejected
> "EHLO debian": "503 5.0.0 Need LHLO here."
> 
> Maybe Tom or someone else of dspam can help here?
> 
> 
> 
> 
> On Monday, June 9, 2014 12:26 PM, Reindl Harald
> <[email protected]> wrote:
> 
> Am 09.06.2014 12:02, schrieb ML mail:
>> Thanks to your help, I think I have found where DSPAM should get
>> called for my setup: in the postfix before-queue content filter. I
>> found the following documentation on postfix which explains quite
>> well how to set this up:
>> 
>> http://www.postfix.org/SMTPD_PROXY_README.html
>> 
>> they also state that it should work with any content filter as long
>> as it speaks SMTP. What do you think? I have the feeling that's
>> exactly what we need for our similar setup.
> 
> sounds damned good, especially the "with any content filter" because
> it makes the components flexible and if i am not completly wrong you
> could even use more than one content filter that way for whatever
> reason
> 
> please report back how it works, as said: i start my project with the
> RHEL7/CentOS7 release because i won't back to the outdated versions
> in CentOS6 using everywhere else Fedora
> 
> possible is it for sure, other spam filter solutions are typically
> not implemented by god nor 1005 self written :-)
> 
> 
> 
> 
>> On Monday, June 9, 2014 11:38 AM, Reindl Harald
>> <[email protected]> wrote:
>> 
>> Am 09.06.2014 11:13, schrieb ML mail:
>>> In my understanding content filtering such as dspam should also
>>> happen before the transport table/map is being checked for
>>> relaying the mail to the backend mail server but then I must be
>>> missing a parameter again for that which is not explained in the
>>> doc/relay.txt of the dspam package. The documentation only 
>>> mentions using virtual transport which I also have configured.
>> 
>> uhm - as said - i consider using dspam and only a heavy postfix 
>> user but until now not for mail-filter-gateways with multiple 
>> destination servers
>> 
>> at least "transport_maps" and "virtual_transport" combined may not
>> work as expected because whatever the first transport is wins - in
>> my understanding dspam needs to work inside of smtpd_*_restrictions
>> and any transport happens if a message passes all filters and
>> restricitions
>> 
>> however - *how* can dspam work as *pre-queue* filter in context of
>> lmtpd? does it receive the whole message, let the connection open
>> due scanning and if it is spam rejects it? pre-queue is important
>> to not get a backscatter
>> 
>> please consider asking that in detail on the postfix-uers list 
>> because there are a lot of expierienced users, i am not at the 
>> point testing this since i wait for CentOS7 and in general your 
>> goal is very similar to my plans
>> 
>>> Below is the output of y postconf -n:
>>> 
>>> alias_database = hash:/etc/aliases alias_maps =
>>> hash:/etc/aliases append_dot_mydomain = no biff = no 
>>> config_directory = /etc/postfix inet_interfaces = allowed 
>>> mailbox_command = procmail -a "$EXTENSION" mailbox_size_limit =
>>> 0 mydestination = mx.domain.tld, debian, localhost.localdomain,
>>> localhost myhostname = debian mynetworks = 127.0.0.0/8
>>> [::ffff:127.0.0.0]/104 [::1]/128 myorigin = /etc/mailname 
>>> readme_directory = no recipient_delimiter = + relayhost = 
>>> smtp_tls_session_cache_database =
>>> btree:${data_directory}/smtp_scache smtpd_banner = $myhostname
>>> ESMTP $mail_name (Debian/GNU) smtpd_tls_cert_file =
>>> /etc/ssl/certs/ssl-cert-snakeoil.pem smtpd_tls_key_file =
>>> /etc/ssl/private/ssl-cert-snakeoil.key 
>>> smtpd_tls_session_cache_database =
>>> btree:${data_directory}/smtpd_scache smtpd_use_tls = yes 
>>> transport_maps = hash:/etc/postfix/transport 
>>> virtual_mailbox_domains = mydomain.com virtual_mailbox_maps =
>>> pgsql:/etc/postfix/vmailbox.cf virtual_transport =
>>> lmtp:unix:/run/dspam.sock
>>> 
>>> On Monday, June 9, 2014 10:17 AM, Reindl Harald
>>> <[email protected]> wrote: Am 09.06.2014 09:50, schrieb ML
>>> mail:
>>>> I was assuming that this relay guide was a full howto, my bad.
>>>> 
>>>> Now as pointed out by yourself and Reindl I have added a
>>>> transport table to my postfix configuration in order to relay
>>>> the mails to the backend server. For that purpose I have added
>>>> the following configuration to postfix:
>>>> 
>>>> transport_maps = hash:/etc/postfix/transport
>>>> 
>>>> The content of my transport file looks like this:
>>>> 
>>>> mydomain.com        smtp:mybackendserver.domain.tld
>>>> 
>>>> 
>>>> The problem here with this new configuration is that my postfix
>>>> does not pass the mail to dspam anymore for scanning, so the
>>>> mail simply goes through directly unscanned to the backend
>>>> server. Am I missing something else?
>>> 
>>> i am currently not a dspam user but considering it in exactly
>>> such a setup and would expect it to work a *pre-queue* filter
>>> which is the only correct way of reject spam which normally means
>>> the transports after the spamfiler because the filter belongs in
>>> smtpd_*_restricitions somehow
>>> 
>>> maybe the output of "postconf -n" could help to fugure out your
>>> setup
>>> 
>>> the reason why i plan such a setup is:
>>> 
>>> * dedicated MX as filter repalcing a Barracuda Networks
>>> appliance * different target servers per domain solved with a
>>> transport table * the final destinations are dbmail and so all
>>> infos already in mysql * a simple script should maintain the
>>> local users table and transports
>>> 
>>> my planned order:
>>> 
>>> * postscreen / rbl scoring * maybe greylisting * clamav * DNS
>>> whitelists to bypass contentfilter * contentfilter (dspam,
>>> spamassassin...) * transport table to deliver ham to final
>>> destiantion
> 
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