I'd like to setup postfix as an MTA for 2 domains, about 10 users each. I'm a bit confused with the documentation. Postfix has so many options for mail delivery. I'd like to have a simple file where I would store all the email addresses (and possibly their corresponding mailboxes). I wouldn't like neither system's passswd file nor mysql to be used for storing email users. What parts of documentation I should be focused on?
Postfix Virtual Readme is the mandatory starting point and covers what you are trying to do, then google for more (ie: distro specific instructions, etc).
There are many tutorials out there, all slightly different, most use a database like mysql as backend, but if you understand the postfix concept of maps then using plain text files is no different.
As totaam said, the virtual readme is the place to start, more specifically the separate domains, non-UNIX accounts example therein.
The extracted example from the documentation is as follows:
/etc/postfix/main.cf:
/etc/postfix/vmailbox:
/etc/postfix/virtual:
The documentation is rather self-explanatory, but in the interest of the community, please comment on your resolution to add to the site and answer content.
I would have recommended the ISPmail tutorial or VBoxAdm, but since you don't wan't MySQL these links probably won't help you much. Maybe you want to check them out anyway to get a deeper understanding of how Postfix handles Virtual Mailboxes.