External connection to Postfix problem

[Imre Gergely]

On 06/20/2013 06:23 PM, Gary Brinker wrote:
> Hello, I'm new to this group but was prompted to try your thoughts on
> the following message I posted to the Postfix user group, where they
> suggested it was not a postfix issue and I should try here. I'm not a
> Linux expert but believe I have all firewall filters off. Thanks for any
> suggestions.
> Gary
>  
> Because of a hardware failure on an old installation of a postfix
> gateway I took the opportunity to install an up to date version on an
> Ubuntu server. I am not too far into the configuration but am having a
> basic problem with accessing it from external sites. I think I can
> eliminate the usual DNS and router configurations as it did work
> correctly with the old system.
> The issue is that I can telnet into it internally with no problem but
> cannot reach it externally. I hooked up wireshark and if I'm
> interpreting it correctly I do find the initial SYN come in but no
> connection is established. My reading suggests that I may have an
> ownership or permissions problem, but I'm not finding success in
> isolating the issue.
> Can anyone point out specifically what I should be looking at to
> diagnose and correct this so I can get on to the meat of the configuration.

I would check some basics first.

Is postfix listening on the external IP address? If not, see
inet_interfaces in main.cf (man 5 postconf)

sudo netstat -nlp |grep master |grep tcp

Is the firewall really off? Try this:

iptables -I INPUT 1 -p tcp --dport 25 -j ACCEPT

This should accept connections to the SMTP port from anywhere.

-- 
Imre Gergely
http://havaz.net
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