Sending Mail Via Postfix Woes
 

Hello there. I recently installed ubuntu and ispconfig3 following one of those "perfect server" guides. Everything appeared to go smoothly. However, when connecting to my email accounts on the server through thunderbird, I can receive email but cannot send email. I can send and receive email via the webmail webpage. Postfix is operating on port 587 as I'm on comcast and that's what they require for outgoing mail. The error that I get in /var/log/mail.log:
and the error that I get in thunderbird:
I imagine that it's a misconfiguration of dovecot or postfix but as I'm new to linux and system administration, I have no clue regarding how to fix the issue or how to go about troubleshooting the issue.

Any advice on the issue is greatly appreciated.

Is this a server on the internet or your home PC?

You are not showing any log lines that would be related to an incoming SMTP connection from an external host. On the other hand, are you sure that the name 'mail.domain.com' (replace with your name) gets mapped to your server? You said you can receive mail but there are no connections from outside in your log snippet.

This is a server on my home LAN. I was running thunderbird from another machine in my LAN. As far as relevant log lines, what log should I post the contents of (or at least a cat | tail )? I'm new to linux and server administration and started this as a hobby so any guidance is greatly appreciated. My mynetworks parameter in /etc/postfix/main.cf which I believe might be relevant is I have tried adding 192.168.1.0/24 to this variable thinking that perhaps no auth attempts were made because they never made it to the auth daemon due to being blocked by this parameter and noticed no difference. I have since reverted my addendum.

What else can I try and what logs should I be looking at?

Well, 127.0.0.1 is the localhost address, and 192.168.1.x is your network. In your log there is no login attempt from a 192.168.1.x address.

What is the address you are trying to connect to from the client PC?

The LAN IP of my server is 192.168.1.9 and the LAN IP of the machine which I'm running thunderbird on is 192.168.1.7.

Edit: I think it's also important to know that I am accessing my server through the MX record of my domain, not the lan address of the server machine.

Yes that is important, because it might not resolve correctly. Have you tried to replace the host name with the IP address?

I just tried your advice and I couldn't log into my email account on the server because it didn't recognize my account name and password combination.

The output of sudo cat /var/log/mail.log | tail -n 30 after attempting to connect:

I did not ask you to change your username, just the mail server address. And do not use SSL/TLS while you are still testing your connection.

Configure TB with :

User Name = nicholas@your.domain (exactly as set up in ISPConfig, do *not* use the IP address here!)
Server Name = 192.168.1.9
Connection Security = NONE
Authentication Method = Normal Password

Use the same settings for incoming and outgoing server!

Then receive and send mail and post your Postfix log again.

Whoops. I didn't realize I had changed my username. Thanks for pointing that out. I did as you have instructed and here are the results:

Thunderbird's error:
cat /var/log/mail.log | tail -n 15:
The error from Thunderbird comes up immediately after trying to send an email. It appears to have received without error.

Ok, receiving seems to work but Postfix is most probably not listening on port 25. Can you post the output of 'postconf -n' please.