I am managing an iRedmail server which hosts multiple user mailboxes. From time to time, I need to disable a particular user's mailbox so that it accepts no incoming emails, for various reasons including that the user's subscription has expired, but external sources still send emails to his mailbox.

The goals I have in mind are:
1 keep the mailbox's existing data, so that I can access its data in case the user reactivates his subscription;
2 bail out of the Postfix pipeline as early as possible, so that these unwanted emails don't consume much server resource;
3 disabling/enabling mailbox should be fully automated, like flipping a bit on/off in the DB.

Any suggestion on how I can achieve this?

Thanks a lot in advance!