Often seeing table hash .../poplock... has changed -- restarting

I am seeing this in the mail logs every few minutes:

Sep 18 14:37:58 jedi postfix/smtpd[56365]: table hash:/var/spool/postfix/plesk-pop/poplock(0,lock|fold_fix) has changed -- restarting

Sep 18 14:37:58 jedi postfix/smtpd[56368]: table hash:/var/spool/postfix/plesk-pop/poplock(0,lock|fold_fix) has changed -- restarting

Is that normal?
Thanks, -t