Vieri Di Paola:
> Hi,
>
> I'm using postfix as an smtp filter (antispam) which then forwards the
> messages to another mail server with user mailboxes.
>
> This server has private IP addr. 10.0.0.1, and the mailbox server has
> private IP addr. 10.0.0.10.
> So, external e-mails are first received by this filter and then
> forwarded to the mailboxes.
>
> It has been working fine for years, but a few days ago some e-mails
> were not coming in anymore, and the logs on the filtering server show
> messages such as this one:
>
> postfix/smtp[13093]: A306E1240B1: to=<m...@mydomain.org>, relay=none,
> delay=0.06, delays=0.06/0/0/0, dsn=5.4.6, status=bounced (mail for
> 10.0.0.10 loops back to myself)
What has changed?
> I'm still trying to understand what that means exactly.
1) It means that postfix/smtp[13093] received a request to deliver
mail for mydomain.org.
***Perhaps it should not have received that request.***
2) It means that postfix/smtp[13093] looked up the MX for mydomain.org
and found that Postfix itself (through the inet_interfaces and
proxy_interfaces parameter values) is MX for mydomain.org.
***Perhaps inet_interfaces or proxy_interfaces are in error.***
Either way, the Postfix SMTP client will not deliver mail to an IP
address that Postfix is already receiving mail on.
> # grep mydomain.org /etc/postfix/*
> /etc/postfix/main.cf:proxy_interfaces = mail1.mydomain.org mail2.mydomain.org
Note: that makes the proxy_interfaces dependent on /etc/hosts, DNS,
and so on. All of these can change without ever touching Postfix
code or configuration.
> /etc/postfix/transport:mydomain.org smtp:[10.0.0.10]
I would not analyze this without a proper diagram. One Postfix
instance that delivers mail to itself is an invitation for mailer
loops.
Wietse
