I installed Postfix on my debian development machine. Easy Peasy.

This dev box sits behind a NAT router and even though postfix is installed, when I try and send email using 'mail' and then at the mail queue with mailq I see 'connection has failed'.

I read this article several times:

http://www.akadia.com/services/postfix_mta.html

I essentially just want to send email to a remote email server using sendmail. I don't need SMTP daemon running as my server should never relay or accept incoming emails. I construct emails using PHP and just want to pass them to sendmail binary for immediate sending (or queueing).

Unlike when I used mail or tried to send an email using telent and SMTP -- when I follwed the example in the above article and used sendmail -- I received no error but no email either.

How do I test or determine what is going wrong with the Postfix sendmail???

I think you are a little confused on the sendmail issue. Postfix uses a "sendmail" command for compatibility with older applications that were expecting the proper Sendmail to be installed. As far as I'm aware, this uses smtp anyway.

I'm sure you can restrict Postfix to local mail only (ie no smtp), but not really an issue. Postfix by default shouldn't be open, so make sure you have your smtpd_recipient_restrictions correct (the default should be OK - permit_mynetworks, reject_unauth_destination) and here's the key - make sure your mynetworks is correct. Assuming you are on a private IP range, and you router/firewall isn't letting spoofed private IP's through, then you should be OK, but explain your network structure if you aren't sure. Read the docs at postfix.org on the restrictions shown above

On the router, it's one thing to open port 25, but note that you will need to forward it from the external IP to your server on your router somehow. Ho depends on the model of course.


Hope that helps