[Dovecot] Corrupted index cache files

[Mike Abbott]

I re-ran imaptest on an empty mail store, single client, multiple  
users, using your dovecot-crlf input file, for a couple hours.  Here's  
the distribution of errors that imaptest reports:
  100 Error: user%d[%d]: <...>: Header DELIVERED-TO changed
  167 Error: user%d[%d]: <...>: Header CC changed
  417 Error: user%d[%d]: <...>: Header TO changed
  438 Error: user%d[%d]: <...>: Header IN-REPLY-TO changed
  445 Error: user%d[%d]: <...>: Header REFERENCES changed
  485 Error: user%d[%d]: <...>: Header FROM changed
  503 Error: user%d[%d]: <...>: Header SUBJECT changed
  544 Error: user%d[%d]: <...>: Header MESSAGE-ID changed
  764 Error: user%d[%d]: UID=%d INTERNALDATE changed
  823 Error: user%d[%d]: UID %d changed
1040 Error: user%d[%d]: uid=%d <...>: BODY changed
1052 Error: user%d[%d]: uid=%d <...>: BODYSTRUCTURE changed
1546 Error: user%d[%d]: uid=%d <...>: ENVELOPE changed
1833 Error: user%d[%d]: uid=%d <...>: RFC822.SIZE size changed
3493 Error: user%d[%d]: uid=%d <...>: BODY[] size changed
3691 Error: user%d[%d]: uid=%d <...>: BODY[HEADER] size changed
3695 Error: user%d[%d]: uid=%d <...>: BODY[TEXT] size changed
3880 Error: user%d[%d]: uid=%d <...>: BODY[%d] size changed
376365 Error: UIVALIDITY changed: %d -> %d

During that time dovecot reported no corruption errors.

What does it mean that imaptest is having such trouble?