The following error message sometimes appears on my server log,it causes the mailbox to exceed the disk capacity limit.

May 9 09:54:11 imap dovecot: imap(hfh@cndns.com): Error: dict-client: Lookup 'priv/quota/storage' failed: Connection closed: read(size=8192) failed: Connection reset by peer (reply took 2.728 secs (2.729 in dict wait, 0.000 in other ioloops, 0.000 in locks))