[quentusrex]

It seems that the file /home/vmail/domain/user/maildirsize is not being updated with the new quota size when the quota is changed by ISPConfig. The hack that seems to fix it is to run the commands:

maildirmake -q {quota}S /home/vmail/domain/user/
chown vmail:vmail /home/vmail/domain/user/maildirsize

right after the quota is changed. I don't know where to add this hack to ISPConfig to fix the bug, if this is even the right hack to do it.