ispcp + postfix + dovecot

[Qwerty256]

You need less packages than in your solution, you don't need to use dovecot you can still use courier-pop3 and courier-imap instead of dovecot, the thing is that postfix and courier-pop3 and everything will get information about users from ispcp database, not from filesystem. for example in my old configuration without dovecot i have courier-imap using only ispcp database for authentication, and postfix is getting from database too i have commented all ispcp-mbox-mngr and this script doing nothing on my filesystem