did you by any chance copied the codes from the site?
you will might have problem because of that.
if you want to understand i really recommend the follow:
just to make sure you can make your server run with no sophisticated settings.
then get into
the only different between OPENBSD and ubuntu is how you install the package
just use the
and you will might want to look at:
apt-get postfix courier-base courier-doc courier-imap courier-imap-ssl courier-pop courier-ssl courier-authlib courier-authlib-mysql courier-authlib-userdb postfix-mysql libsasl2-2 libauthen-sasl-perl