Postfix-Server behind a DSL-Router

[Peter Ulrich Kruppa]

Am 09.04.2015 um 22:05 schrieb Mike Wright:
>
>
> On 04/09/2015 01:01 PM, Peter Ulrich Kruppa wrote:
>>
>>
>> Am 09.04.2015 um 21:53 schrieb Mike Wright:
>>>
>>>
>>> On 04/09/2015 12:46 PM, Peter Ulrich Kruppa wrote:
>>>>
>>>> Am 09.04.2015 um 21:30 schrieb Mike Wright:
>>>>>
>>>>> 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
>>>
>>> Yes. Between these two there should have been a reply from you,
>>> pukruppa.de.smtp > mail-wi0-f177.google.com.35438.
>>>
>>>> 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?
>>>>
>>> Which side of your router are you listening on, public or private?
>> Hmmmh,
>>
>> I am quite new to Fedora, but enp4s6 should be the NIC which connects my
>> server to my router. So it is the private side of my network, isn't it?
>
> That only tells me that it is the network card on your computer.  I'm
> guessing that you haven't moved it and you are still connected to the
> inside of your router and have a non-routeable IP.  If that is true your
> mail server does not appear to be answering requests.
Yes, it is my router, which has the routable outside IP - my server's 
NIC enp4s6 has the private 192.168.10.1







>
>>
>>
>>> If it's the public side that only shows that mail and dns are working
>>> from outside.  Now you have to test from inside.
>>>
>>> If it's the private side it says mail is making through and your mail
>>> server is not answering.