How to customize "mailbox full" bounce message?

I'm not queuing mail for users with full inboxes on most of my servers. How do I customize the message received by sender when an email bounces because the user's mailbox is full?

Example of what they get now

Code:

This message was created automatically by mail delivery software.

A message that you sent could not be delivered to one or more of its
recipients. This is a permanent error. The following address(es) failed:

  XXX@XXX.net
    mailbox is full

Example of what I what I would like it to say

Code:

This message was created automatically by mail delivery software.

A message that you sent could not be delivered to one or more of its
recipients. This is a permanent error. The following address(es) failed:

  mark@sysops.neathosting.net
    mailbox is full

Please try resending your message again in one day's time. Hopefully the user will have downloaded or cleared their inbox by then.

or even...

Code:

This message was created automatically by mail delivery software.

A message that you sent could not be delivered to one or more of its
recipients. This is a permanent error. The following address(es) failed:

  mark@sysops.neathosting.net
    mailbox is full

Have you tried telephoning this person as obviously they don't know how to manage their inbox?

Any help would be appreciated.

 

I would still love to do this - an exim config experts out there?