[Dovecot] What best decision to make for flatfiles or SQL when I use Dovecot2 + Postfix together?

[terryjames9461 at mm.st]

Hello,

I'm moving my mail server from Exchange to an opensource one.

After a bunch of reading, I decided on building a Dovecot2 + Postfix
server in a VirtualUsers-only + Multiple-domains configuration.

Since my messages will be stored by Dovecot, and the documentation is
really good, I figured that it's smartest to configure Dovecot, then
make Postfix 'fit' to it, sharing the data files that way.

I read through lots of the Dovecot wiki for v2.

There are many ways for storing the database data.  My goal is to only
have data in one instances, used by both Postfix & Dovecot.

I'm a little confused about: to do that sharing-in-one-place, do I have
to use SQL or can I use the flatfiles like passwd-db?   I think for sure
someone already decided the best approach for this, and maybe I'm not
understanding the logic to it.

The data I think I need to share are:

 users (user at domain.com)
 passwords
 user aliases (mapping user2 at domain.com -> user1 at domain.com)
 domains
 domain aliases (domain.com also receives email for domain2.com)

And I think all of this can be in passwd-db in Dovecot.  But I also want
to make sure that Postfix ONLY accepts email for users/domains that
exist, so it has to read that data too.

Can I do this that way with the flatfiles?  Or do I have to use the SQL
approach?


TJ