Postfix-Server behind a DSL-Router

[Andy Blanchard]

SMTP from external IP addresses (e.g. anything other than 127.0.0.1)
is blocked by default by the Fedora firewall and I've not seen any
mention of checking that in the thread.  I'm assuming you are using
the default firewall, FirewallD, rather than iptables?

If so:

"sudo firewall-cmd --get-services" will list supported services.  SMTP
should be on the list.
"sudo firewall-cmd --zone=public --list-services" will list permitted
services in the public zone.  SMTP should also be on the list.
"sudo firewall-cmd --zone=public --add-service=smtp" will temporarily
add SMTP to the permitted services if not present above.
"sudo firewall-cmd --permanent --zone=public --add-service=smtp" will
make that change permanent (survive a reboot).

If you are using iptables, then you can check the rules with:

"sudo iptables --list-rules"

You should have an entry that reads something like:

"-A INPUT -p tcp -m tcp --dport 25 --tcp-flags SYN,RST,ACK SYN -j ACCEPT"

If not, you can add it by editing the file "/etc/sysconfig/iptables",
adding the line above to the INPUT chain, then reloading the rules
with the command "sudo iptables-restore < /etc/sysconfig/iptables".

HTH

On 9 April 2015 at 11:07, Peter Ulrich Kruppa <pukruppa at googlemail.com> wrote:
> Hi everyone,
>
> please do excuse my unspecific subject - I don't really know what my
> problem is yet.
>
> I set up a Postfix-Server on my Fedora 21 box, which is connected to
> the internet via
> some Netgear Router. My private LAN is 192.168.10.0/24 with the Fedora
> box fixed on
> 192.168.10.1 . My Netgear thing has got a fixed IP and hostname, let's say for
> mydomain.com .
>
> Now I can
>   - send myself mails from my Fedora box
>   - send mails from my Fedora box to the outside p. ex. my googlemail account
>
> but I can't receive mails from outside.
>
> When I do a
>     # tcpdump -n -i any tcp port 25
> on my Fedora I can see many messsages like
>
> 10:34:09.338691 IP 212.227.17.11.64945 > 192.168.10.1.smtp: Flags [S],
> seq 3273717964, win 14600, options [mss 1418,sackOK,TS val 1273019143
> ecr 0,nop,wscale 9], length 0
> 10:34:10.339378 IP 212.227.17.11.64945 > 192.168.10.1.smtp: Flags [S],
> seq 3273717964, win 14600, options [mss 1418,sackOK,TS val 1273019393
> ecr 0,nop,wscale 9], length 0
> [...]
>
> Any good ideas, what else I can do to analyze my problem?
>
> Thanks for your answers
>
> Peter
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-- 
Andy

The only person to have all his work done by Friday was Robinson Crusoe