basically the qmail package in ubuntu kinda works, but things are in really unusual places, so for your sanity you should probably hand crank your qmail install.
If you don’t, you’ll want to replace the defaults in /var/lib/qmail/aliases for .qmail-default .qmail-postmaster and .qmail-root as the automagic install tries to do something fancy with an alias user who doesn’t exist.
smtproutes is your friend if you want to use qmail to forward email… ssmtp is my goto but my favorite monitoring package nefu doesn’t work with ssmtp, so I’ve taken to installing qmail everywhere.
/var/lib/qmail/control/smtproutes (it’s /var/qmail/control/smtproutes for sane installs)
to forward all email to said host, or you can use an ip like this
also you can make it only listen to localhost (avoid adding yet another open relay to the internet) by editing
and changing the 0 before smtp to 127.0.0.1
qmail is kindof complex to control, so when in doubt kill everything off, and let svnscan, runsv, or what ever is keeping an eye on qmail processes restart them for you… again for your sanity you should roll your own or use qmailtoaster on centos (I mean how hard is it to create an init script that behaves the way that you’d expect?)