Alright, here we go:

*) WARNING: Please test your code on a testing machine first, don't do it on production server directly. Removed mailboxes CAN NOT be restored.
*) We're taking the latest iRedAdmin-Pro-LDAP-1.6.3 for example. If you haven't upgraded to 1.6.3, please upgrade it as soon as possible.
*) Open file libs/ldaplib/user.py, find function 'deleteSingleUser()', about line 328:

    # Delete single user.
    def deleteSingleUser(self, mail, deleteFromGroups=True,):
        ...

        try:
            ...
            # Delete object and its subtree.
            deltree.DelTree(self.conn, self.dnUser, ldap.SCOPE_SUBTREE)
        ...

What you need to do are:

*) Query LDAP server to get maildir path of this mail user.
*) Delete the whole maildir directory. Note: It will execute command as user 'iredadmin' and group 'iredadmin' by default, so please make sure this user/group can access mailbox directory (/var/vmail by default).

All your code MUST be placed ABOVE line 'deltree.DelTree()' i paste above.
To delete whole mailbox directory, you can use Python module 'os'. For example:

import os
os.removedirs('/tmp/test_dir/')

Did you ever get this working?

I completely agree that iredadmin does not delete the user files straight away when a user gets deleted.
But I also see how this can become a big issue on small filesystems. So I would suggest a compromise using a daily cron job which delete user email directory if it no longer exists in the databae.
- For security this would save the users email directory for 30 days by:
1. When it first notices that the user no longer exists in the DB write a file with the current date or using a counter which gets decremented each day.
2. For each "deleted user" this date is then compared to the CURRENT_DATE and if it is more then 30 days delete the directory.

This keeps everybody happy :-)

Excellent!

I was just about to revive my thread to inquire about the status of this.
We launch live this Sunday!

Is there any chance I can get a quick how to so I can implement the change prior to the launch?

If not we can wait, however It would of great use to us so that we can implement the changes while the server is dormant and inactive.

Either way, the support is phenomenal. It is very much appreciated.