ispcp + postfix + dovecot

[ephigenie]

yes sure i'm aware of that.
I did qmail and qpopper / exim setups with mysql long before anybody was talking about it.
But the thing with generated files remains.
It might be true that on the one hand it introduces an unnecessary level of complexity - on the other hand it is also kind of safety redundancy.

However if dovecot is available as a debian package, the best solution would be to give users a choice while they install. At that point they can even decide if they want the extra redundancy of having the account data written in files or if they want to have it in the database.

If you prepare the complete dovecot side, i can take care of the installer.