[CentOS] setting up postfix

[Andy Smith]

On 16 October 2012 17:14, Larry Martell <larry.martell at gmail.com> wrote:

> On Tue, Oct 16, 2012 at 8:58 AM, Joseph Spenner <joseph85750 at yahoo.com>
> wrote:
> >
> >
> >
> > ________________________________
> >  >From: "m.roth at 5-cent.us" <m.roth at 5-cent.us>
> >>To: CentOS mailing list <centos at centos.org>
> >>Sent: Tuesday, October 16, 2012 7:49 AM
> >>Subject: Re: [CentOS] setting up postfix
> >  >
> >>Larry Martell wrote:
> >> This should be an easy one. I'm trying to get postfix going. I've
> >> never done this before. I followed the directions at
> >> http://wiki.centos.org/HowTos/postfix. I opened port 25:
> >>
> >> iptables -I INPUT -p tcp -m tcp --dport 25 -j ACCEPT
> >>
> >> But I don't receive the mail. In a file in /var/spool/postfix/defer I
> see:
> >>
> >> alt2.gmail-smtp-in.l.google.com[2607:f8b0:400d:c00::1a]:25: Network is
> >> unreachable
> >>
> >> Have I missed a step or done something wrong?
> >>
> >
> > Have you tested to see if tcp/25 is really open?  From another system:
> >
> > $ telnet ip.of.postfix.box 25
> >
> > Do you get a sendmail/postfix message of some sort?
>
> No, I can't connect:
>
> # telnet 10.188.36.207 25
> Connecting To 10.188.36.207...Could not open connection to the host, on
> port 25:
>  Connect failed
>
> iptables shows that port open:
>
> Chain INPUT (policy ACCEPT)
> target     prot opt source               destination
> ACCEPT     tcp  --  anywhere             anywhere            tcp dpt:smtp
>
> Chain OUTPUT (policy ACCEPT)
> target     prot opt source               destination
> ACCEPT     tcp  --  anywhere             anywhere            tcp dpt:smtp


Hi.

It seems you are telnetting using- and have firewall rules for- an IPv4
network.
Your postfix seems to be trying to use IPv6. :
alt2.gmail-smtp-in.l.google.com[2607:f8b0:400d:c00::1a]:25: Network
is unreachable.

Does the client's network and ISP use IPv6?

Have you tried configuring inet_protocols = ipv4 in the main.cf ?
Your box might be configured with IPv6, but that doesn't mean it is usable
on the network.

OT: The default policies of your chains appear to be "ACCEPT" - thus if
there is no REJECT or DROP rule matching your SMTP connection, it will be
automatically accepted when it hits the bottom of the chain, regardless of
what ACCEPT rules you apply.

Regards,
  Andy.