[Dovecot] Error: Maximum number of mail processes exceeded (see max_mail_processes setting)

Hello

I have this message repeated several times each *seconds* in /var/log/dovecot/dovecot.log

the max_mail_processes is set to 8192 and I can see an average of 500 imap processes on the machine , I think there is a problem somewhere ...

Debian 64 bits , IBM X3650 biproc , 7 Gb RAM , RAID5 disks , 2 ethernet Gb ports bonded.

Dovecot 1.1.11 has been compiled from scratch on the machine

Thanks for any info.