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postfix-users: Re: Backup MX whitelisted by primary MX: Open hol

Re: Backup MX whitelisted by primary MX: Open hole for spam?

From: <lists_at_nospam>
Date: Sat May 10 2014 - 09:35:56 GMT
To: postfix-users@postfix.org

Am 10.05.2014 06:35, schrieb deoren:
> Setup:
>
> * backup MX with light anti-spam policies (for the moment)

the root of all evil is by setup a backup MX at all

there is a reason why smtp servers retry later if the destination
is down and that fact is even used for greylisting to reduce spam

> * primary MX with current policies. Also whitelists the backup MX via check_client_access directive and via
> permit_mynetworks
>
> Question:
>
> If a spam email makes it "in" through the backup MX and is delivered to the primary, will the 'permit_mynetworks'
> or 'check_client_access' directives prevent other checks from blocking the email? In other words, do those two
> directives only apply to mail that originates from the backup MX itself or all mail that flows through it?

nobody knows because nobody knows wat is in that configurations
"check_recipient_access" in any ways is dangerous

empty "smtpd_recipient_restrictions" is not really smart
why are you doing that instead configure them and place the
line *below* permit_mynetworks?

check_recipient_access, check_sender_access and check_client_access
with no relay and smtpd restricitons before makes you sooner or
later to a open-realy, why was discussed here many times

> Settings on the primary MX:
>
> smtpd_recipient_restrictions =
> permit_mynetworks
> reject_unauth_destination
> check_recipient_access hash:/etc/postfix/recipient_access.conf
> check_sender_access hash:/etc/postfix/sender_access.conf
> check_client_access hash:/etc/postfix/client_access.conf
> check_policy_service inet:127.0.0.1:10023
> reject_invalid_helo_hostname
> reject_non_fqdn_helo_hostname
> reject_unknown_client_hostname
> reject_unknown_sender_domain
> reject_unknown_recipient_domain
> reject_non_fqdn_sender
> reject_non_fqdn_recipient
> reject_unauth_pipelining
> reject_rbl_client zen.spamhaus.org
> reject_rbl_client b.barracudacentral.org