I have a question about the function of the relayPort variable. I 
apologize for the long text ;)

I'm running a test setup using two servers, both running Debian 8.6 and 
Postfix. One is the 'end user' mail server (, the other 
Postfix + ASSP (

"Normally", a server on the lan that needs to be able to relay mail to the 
internet would be placed in acceptAllMail. By default ASSP listens on port 
25 for mail from the lan to the internet (Postfix runs on port 125 on the 
ASSP machine). So in my end user mail server I have "relayhost =" and that works fine: if I send out a mail I see it passing 
through ASSP (not running as a daemon but showing everything in the 
console). So far so good.

On my production server however I have relayPort set to 225 and my IBM 
Domino mailservers use *that* port to relay outgoing mail through ASSP. 
The production ASSP server also runs Postfix on port 225.

Now as I understood it, relayPort is meant to be an extra port, sort of 
like security through obscurity, that allows you to relay outgoing mail on 
a non-standard port. The fact that this is working in my production 
environment corroberates that.

Now, if I set relayPort to 225 in my test setup and put (the 
'end user' mail server) in allowRelayCon (it is also still in 
acceptAllMail) and on my mail server change relayhost to 
(and reload or even restart Postfix) then mail is not relayed by ASSP. It 
leaves the mail server but it doesn't get picked up by ASSP. Restarting 
ASSP or rebooting the ASSP server does not change this. If I do netstat 
-tulpn | grep 225 on the server I can see that port 225 is not open. 
(Interestingly it also seems not to be open on my production ASSP machine 
while I'm pretty sure that *does* work.) If I change things back the mail 
gets delivered.

Here comes the part where it gets confusing: when changing the relayPort 
value, a green line underneath the value box is shown reading: "relayHost 
() and relayPort (225) must be defined to enable relaying". Aha. 
relayHost, if I am not mistaken, has to do with mailservers upstream from 
ASSP: your isp's relay server. Suddenly we go from relaying mail 
internally to relaying mail to an outside server. We go from within the 
lan to outside.

My question here is: why do I need to set up relaying to a server at my 
isp's (which they haven't) when I all I want to do is set up relaying from 
my 'end user' mail server to my ASSP box? Those have got nothing to do 
with each other.

Thank you in advance for any enlightenment you can bring me on this 

Have a great day :)

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