Looks like a good resource. The one I worked from had MySQL backed accounts and postadmin set up (+ a bunch of anti spam / anti virus stuff)
It looks like you have missed out a SASL authentication mechanism. I recommend using Dovecot as it's MUCH easier than getting Postfix to use MySQL directly. But following the above blog post is the easiest thing to do. I read my own blog posts when I have to do these things. ;)
This: 1. Edit*/etc/postfix/master.cf*, uncomment the line for the*submission*service, and restart Postfix. This makes Postfix listen on port 587 which is allowed through most firewalls. It looks like that all along I had not set up 587 on the VM. Thank you for helping me circle back to the obvious! The only thing left to do is set up vacation emails - any suggestions? Preferably with a way for users to manage them themselves (bearing in mind the Dovecot / SASL / MySQL thingo) Cheers Piers