Postfix-Server behind a DSL-Router

[Mike Wright]

On 04/09/2015 11:36 AM, Peter Ulrich Kruppa wrote:
> Am 09.04.2015 um 18:18 schrieb Heinz Diehl:
>> On 09.04.2015, Peter Ulrich Kruppa wrote:
>>
>>> To me this looks as if port forwarding is all-right but Postfix does not
>>> react (?!?)
>>
>> Take a look into the postfix log.
> I can see postfix/master has been started and I can see activities when I
> write myself an  email from my server. But no messages about activities
> from
> outside.

You can try running tcpdump to watch incoming connections while you send 
yourself an email from gmail/yahoo etc.  That will let you know if mail 
is arriving and getting through your firewall.

tcpdump -i eth0 port 25  (assuming single ethernet card).

Are you also hosting your own DNS?  If not you can also try the same 
thing by booting from a thumb drive and listening on your public facing 
IP.  Success will indicate both that your external DNS provider is 
pointing to you and that traffic is getting to your IP.

Mike Wright