Sending Mail Via Postfix Woes

[Wsbs9GC]

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:

Aug 12 05:40:01 www postfix/smtpd[27096]: connect from localhost.localdomain[127.0.0.1]
Aug 12 05:40:01 www dovecot: imap-login: Disconnected (no auth attempts): rip=127.0.0.1, lip=127.0.0.1, secured
Aug 12 05:40:01 www dovecot: pop3-login: Disconnected (no auth attempts): rip=127.0.0.1, lip=127.0.0.1, secured
Aug 12 05:40:01 www postfix/smtpd[27096]: lost connection after CONNECT from localhost.localdomain[127.0.0.1]
Aug 12 05:40:01 www postfix/smtpd[27096]: disconnect from localhost.localdomain[127.0.0.1]
Aug 12 05:45:01 www dovecot: imap-login: Disconnected (no auth attempts): rip=127.0.0.1, lip=127.0.0.1, secured
Aug 12 05:45:01 www postfix/smtpd[27164]: connect from localhost.localdomain[127.0.0.1]
Aug 12 05:45:01 www dovecot: pop3-login: Disconnected (no auth attempts): rip=127.0.0.1, lip=127.0.0.1, secured
Aug 12 05:45:01 www postfix/smtpd[27164]: lost connection after CONNECT from localhost.localdomain[127.0.0.1]
Aug 12 05:45:01 www postfix/smtpd[27164]: disconnect from localhost.localdomain[127.0.0.1]

and the error that I get in thunderbird:

Sending of message failed.
The message could not be sent because the connection to SMTP server mail.domain.com [yes, this has my real domain not a dummy] was lost in the middle of the transaction. Try again or contact your network administrator.

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.

[Sir Henry]

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.

[Wsbs9GC]

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

mynetworks = 127.0.0.0/8 [::1]/128

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?

[Sir Henry]

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?

[Wsbs9GC]

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.

[Sir Henry]

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