Kloxo-MR and Kloxo have different mechanism to handle qmail. Kloxo-MR using qmail-toaster and Kloxo using special qmail. So, solution for Kloxo not always able to implementing to Kloxo-MR.
Please read
viewtopic.php?f=15&t=9426 to make qmail-toaster work perfectly in Kloxo-MR.
If running 'sh /script/fixmail-all' and then reboot still not resolve an issue, possible need reinstall qmail-toaster with step:
# remove qmail-toaster (possible remove some dependencies like fetchmail)
yum remove *-toaster
# delete qmail directories content
rm -rf /var/qmail/*
# install again qmail-toaster
yum install *-toaster fetchmail
# recreate config
sh /script/fixmail-all
# restart service; better reboot
qmailctl stop
qmailctl start
NOTE: - above step not able to implementing to Kloxo 6.1.x because fixmail-all no exists on Kloxo 6.1.12