On 02/15/2011 08:21 PM, John wrote:
First off I am still a bit green on this stuff.
Both my servers are multi-homed, server A which runs Postfix is
configured -> eth0 :n.n.n.186 and eth1:n.n.n.187.
The host name for this server is mail.domain.tld which points to
n.n.n.187.
Up until last Friday we did not have any problems. On Friday we
started to get bounced when we tried to reply to a new contact at
AT&T/Prodigy. Their bounce message is as follows:
"host sbcmx5.prodigy.net[207.115.21.24] said: 553 5.3.0 flpd241
DNSBL:ATTRBL 521< n.n.n.186
>_is_blocked.__For_information_see_http://att.net/blocks (in reply to
MAIL FROM command".
A check of our logs shows only four message destined for their servers
in the last four weeks. I have check our servers using abuse.net and
we do not appear to be an open relay. None of the RBL have us listed.
So I do not think the problem is spamming.
I think the problem is Postfix is sending using eth0, which in turn
means that it appears to come from n.n.n.186, which in turn means that
a reverse lookup does not resolve to mail.domain.tld. The loop is not
closed and therefor we are suspect.
I did some digging around I think that I need to modify my Postfix
configuration by adding "inet_interfaces=n.n.n.186, n.n.n.187,
localhost" and "smtp_bind_address=n.n.n.187". However this is where I
get a little confused as in one set of documents I have read it says
to add these into main.cf, while the postconf.5html say to leave the
inet_interface at default and add the smtp_bind_address the master.cf.
inet_interfaces defines which IPs (and ergo interfaces) postfix RECEIVES
mail on.
This can be overridden per-service by providing the desired IP in the
master.cf service definition.
smtp_bind_address defines which IP postfix uses to SEND mail.
This can be overridden for any outgoing smtp(8) transport.
Unsurprisingly, postconf(5) is correct.
--
J.
