Postfix-Server behind a DSL-Router

[Peter Ulrich Kruppa]

Am 09.04.2015 um 21:30 schrieb 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).
This is, what I see, when an mail from outside arrives:
	# tcpdump -i enp4s6 port 25
tcpdump: verbose output suppressed, use -v or -vv for full protocol decode
listening on enp4s6, link-type EN10MB (Ethernet), capture size 262144 bytes
21:39:21.951957 IP mail-wi0-f177.google.com.35438 > pukruppa.de.smtp: 
Flags [S], seq 4222003974, win 42900, options [mss 1418,sackOK,TS val 
1017047302 ecr 0,nop,wscale 7], length 0
21:39:22.951335 IP mail-wi0-f177.google.com.35438 > pukruppa.de.smtp: 
Flags [S], seq 4222003974, win 42900, options [mss 1418,sackOK,TS val 
1017048302 ecr 0,nop,wscale 7], length 0

Does that say anything to you?

Peter

> 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