[horde] Folder Corruption in IMP

[Steve Devine]

Our Environment:
IMP 4.2.2 - horde-webmail-1.1.5
Courier IMAP 4.4.1  Maildir format

We have had several instances where IMAP folders have "become corrupted"
By this I mean they were working OK and the users were happily storing  
emails in them and then one day they go into this folder and discover  
its empty.
When we look in them the structure is like so:
4K drwx------ 2 XXXXXX 1024 4096 Apr 10 01:40 tmp/
0K -rw-r--r-- 1 XXXXXX 1024   16 Apr  8 14:19 courierimapuiddb
4K drwx------ 2 XXXXXX 1024 4096 Dec  4 08:54 courierimapkeywords/
0K -rw-r--r-- 1 XXXXXX 1024   43 Dec  4 08:54 courierimapacl
0K -rw------- 1 XXXXXX 1024    0 Jan 22  2008 maildirfolder

As you can see the cur/ and new/ directories are gone. In some cases  
the users lost email(s) are in tmp/ but of course these are only going  
to be emails that were added after the corruption occured. The older  
emails in cur are gone.
I tested this behavior in Thunderbird and discovered that as long as  
there is a tmp/ directory the client will move the email with no error  
or complaint. So its not just IMP.
However so far all my users who have filed complaints say they were in  
our IMP installation when all this happened.

So finally I arrive at the question --
Can anyone think of a reason why this (sudden folder corruption) may  
be happening? The unfortunate angle on this is that many of these  
users go weeks without entering the folder itself and don't know that  
the corruption has occurred.

Thanks
/sd

Steve Devine
Email & Storage
Academic Technical Services
Michigan State University