Pulling my hair out ofver Postfix setup

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DMPug

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Aug 27, 2014
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Bear with me; I am new to Linux.

We are trying to setup email servers on 2 Linux boxes for a class (The instructor has no issue with us getting help from forums).

We did a clean install of Ubuntu and then at the instructor's recommendation, we installed Webmin to help with management.

We decided to use Postfix for our email server and are attempting to send mail using an IP address instead of a domain. We can send and receive email from one account to another local account, and we can send email to an outside account, but we can not receive email from an outside account.

Anyone have any ideas on what we may have done wrong or were we can go from here?
 
Solution
ubercake
I'm getting more confused by the last statement.

First, you say:

"We can send and receive email from one account to another local account, and we can send email to an outside account, but we can not receive email from an outside account.

Anyone have any ideas on what we may have done wrong or were we can go from here?"

but then you say:

"I'm not concerned with getting email from the outside world (ie gmail or yahoo) but I would think I coulg get email from another box on my own network"

I'm under the impression you can send mail internally since you say you can send from one local account to another? Please clarify what it is you can do and what you still want to do and we can help you out.

If you want to be able to communicate...
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ubercake

ubercake

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Oct 28, 2009
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This is because the servers on your internal network understand the addressing internally and through external DNS, externally, but anything external does not understand your internal addressing (DNS). You need an IP address or domain and associated IP addressed assigned externally in order for this to work. Dynamic DNS services can work too. Once this is set up, you need to forward all incoming mail traffic (using your router) to your mail server or use the mail server as the server associated with the domain name or external IP address.
 
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DMPug

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Aug 27, 2014
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The setup for this is two linux boxes in a classroom connected over switches and we are trying to send email using @192.168.x.x With this kind of setup do we need to setup a DNS server on our own little network? I would have though that because we are on the same network and using IP address, that DNS would not have been necessary.
 
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Ijack

Ijack

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of course you can't receive mail from the outside world - 192.168.x.x is a private network and is non-routable. There are thousands of networks that use those addresses - how would a mail server know which of those thousands to route mail to (if it could route it, which it can't!).

You might like to read up about port forwarding on your router, which is one way around this problem. You would then send mail to the IP address of the router. But many, if not most, mail servers in the real world will get pretty sniffy about sending mail to a raw IP address. It's the sort of thing that raises suspicion of something funny going on.
 
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DMPug

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Aug 27, 2014
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I'm not concerned with getting email from the outside world (ie gmail or yahoo) but I would think I coulg get email from another box on my own network.
 
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Ijack

Ijack

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Ah. When you said "local" and "outside" I thought you meant local as in "local area network" and "outside" as in outside world.

When you have problems with an email server the first thing that you need to do is to try to establish an SMTP session manually by telnetting to port 25 on the server. http://www.port25.com/how-to-check-an-smtp-connection-with-a-manual-telnet-session-2/

The other thing that you should do is to turn on the highest level of debugging on the postfix server. Between them, the telnet session and the debug logs should help you pinpoint the error.
 
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ubercake

ubercake

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Oct 28, 2009
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I'm getting more confused by the last statement.

First, you say:

"We can send and receive email from one account to another local account, and we can send email to an outside account, but we can not receive email from an outside account.

Anyone have any ideas on what we may have done wrong or were we can go from here?"

but then you say:

"I'm not concerned with getting email from the outside world (ie gmail or yahoo) but I would think I coulg get email from another box on my own network"

I'm under the impression you can send mail internally since you say you can send from one local account to another? Please clarify what it is you can do and what you still want to do and we can help you out.

If you want to be able to communicate with the outside world through e-mail, you need an address that is known outside your network whether it is a static IP, or through a domain name service or dynamic domain name service. This outside address is what other mail services would use as the destination.
 
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Solution
Ijack

Ijack

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Jul 30, 2008
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I interpret the OP's clarification to mean that "local" means between two accounts on the same machine and "outside" means mail from the other mail server.

There are a host of things that you can get wrong and it all depends upon what responses the server is giving. So the OP needs to try a manual session with the server, and look at the Postfix logs with full debugging enabled, to determine what is going wrong.
 
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