DUH! Please ignore the Corrupted index cache file; the "mailbox" in question is a file named delivery.log (i.e. procmail log file) that is in the user's ~/mail directory. Of course there will be problems trying to index this file, it is not an mbox! *sigh*
Hmm. It still seems like there's something Dovecot should do better here. I'll see what I can do about it with my procmail log file :)
How about a configuration option that's a regex or glob of files to ignore in the mail directories?
I second the motion! :-) We have a number users with procmail recipes that put deliver.log in ~/mail. This was not a problem with uw-imap since most of our users would subscribe to their folders, and so they would never see it. Now that Dovecot roots itself in ~/mail we are recommending to our users not to bother with subscribing but instead show all folders, so it is appearing in their folder list by default. A few people have already complained, which means that there are a zillion others who are just muttering to themselves. :-/
Chris