PostfixAdmin and System Messages

[Greg Groth]

After 20 years of Sendmail, I've built a new mail server using the 
guidelines outlined at purplehat.org.  So far, everything is working 
great except that my system messages that used to be delivered to my 
account are MIA.  I do have an alias in /etc/aliases from root to my 
email address hosted on the same server, but I don't know if Postfix / 
PostfixAdmin uses the /etc/aliases when configured to use virtual 
aliases.  I also added a virtual alias from root at domainname.com to 
user at domainname.com

A little more history: In the purplehat.org documentation was the 
following note.

<quote>

If you are receiving errors in your logs about $mydestination, be sure 
that _ANY_ ‘virtual’ domain you are hosting is _NOT_ listed in your 
/etc/hosts file. Apparently this causes a problem being as Postfix 
cannot determine if the domain is virtual or not. (Thanks Valentin)

</quote>

I am only running a single doman on the server, but because of the above 
message, I specifically avoided entering the mail server's internal IP 
address and FQDN in /etc/hosts.  However, when I looked at my maillog I 
noted that Postfix was trying to send the system emails to my mail 
server's outside IP address, which obviously didn't reply.

While I run my own DNS server on the same box as my mail server, it's 
serving the external IP addresses to the outside world.  It's currently 
1 of 2 machines on my DMZ, which has a non-routable IP range of 
192.168.100.X.  Because of there only being two machines, I use 
/etc/hosts for any needed name resolution on the network, and my 
/etc/resolv.conf is pointed at 8.8.8.8 & 8.8.4.4.

Because of this issue, I then decided to try adding an entry to my 
/etc/hosts file :

192.168.100.10        domainname.com        mail.domainname.com

Now when I check the maillog, although it is now finding the mail 
server, I see that my system emails are now being routed to 
root at mail.domainname.com instead of root at domainname.com.

Based on what I'm seeing, I'm assuming that this is more of a DNS issue 
than Postfix, I'm just not sure if I can use the hosts file to fix it or 
if I should try to install a local DNS server just for my DMZ for the 
system emails?   Other than the system emails, everything else has been 
working great.  Any thoughts?

Regards,

Greg Groth