Yes, I mean this, I fallowed your advice:
If you use maildir, you can try to disable the quota procmail recipe. Then the quota is handled completely by the linux system quota. This might solve the problem.
Open the file
and comment out the line:
Then go in the ispconfig interface and change something in an account of y user where you got this problem and save the user. The procmailrc will then be rewritten.
But don't know how to change to all users this ? Not to only 4 one... I have about 600 users
Thanks for advice!