Error: Corrupted record in index cache file

[Orion Poplawski]

With dovecot-2.2.36-3.el7.x86_64 we had a couple hours where mail_plugins did
not properly include zlib for all of the needed services.  This seems to have
led to some corruption in our mdbox mailboxes.

I've run doveadm force-resync on a number of users, but I'm still seeing
messages like this:

dovecot[13563]: imap(USER): Error: Corrupted record in index cache file
/var/spool/imap/USER/mailboxes/INBOX/dbox-Mails/dovecot.index.cache: UID
67976: Broken physical size in mailbox INBOX:
read(zlib(/var/spool/mail/USER/storage/m.1203)) failed: Cached message size
smaller than expected (2978 < 8192, box=INBOX, UID=67976)

Is there anything that can be done about this?  Can I safely delete the
dovecot.index.cache file?  I'm hesitant to do so since I understand that the
mdbox format uses the index to store mailbox information and deleting at least
some index files is a destructive operation.

Thanks!

-- 
Orion Poplawski
Manager of NWRA Technical Systems          720-772-5637
NWRA, Boulder/CoRA Office             FAX: 303-415-9702
3380 Mitchell Lane                       orion at nwra.com
Boulder, CO 80301                 https://www.nwra.com/