service dovecot stop
find /var/qmail/mailnames/*/*/ -type f -name dovecot.index -delete
find /var/qmail/mailnames/*/*/ -type f -name dovecot.index.cache -delete
find /var/qmail/mailnames/*/*/ -type f -name dovecot.index.log -delete
find /var/qmail/mailnames/*/*/ -type f -name dovecot.index.log.2 -delete
service dovecot start