Mail cannot clear Drafts in .OfflineCache but can save to Drafts on server

Question

OK, I've been chasing this problem (and other related issues) for three days now and I'm at wits end.
I see that I am not alone with the the Mac Mail app getting stuck with messages in its .OfflineCache folder for an email account that it can not process. The common response is to quite Mail, and delete the contents of .OfflineCache, if not the whole directory.
In the case in front of me now, I have 7 versions of a draft message (destined for "Drafts"), a delete of that draft message and a copy of that message destined for "Sent Messages". Obviously, for a while Mail could not execute these commands to the IMAP server at SpamArrest.
What I don't understand is why can I continue to save new files to Drafts and Sent Messages but the .OfflineCache cannot clear itself?
I don't want to just delete the files in .OfflineCache (partly because I need the one in Sent Messages) but I because that is just treating the symptom and not fixing the recurring problem of messages ending up .OfflineCache on a fairly regular basis.
Why can't Mail clear the .OfflineCache?

Answer 1

I keep looking at the IMAP protocol output from the Connection Doctor and I'm stymied at why I'm getting a time out. In tracing the log, I see us connect on port 993 with thread 0x187564f0:
CONNECTED May 24 23:00:28.046 [kCFStreamSocketSecurityLevelNegotiatedSSL] -- host:mail.spamarrest.com -- port:993 -- socket:0x1917bbc0 -- thread:0x187564f0
We then start a new thread 0x191581a0 which performs all the subsequent actions including the APPEND:
WROTE May 24 23:00:29.286 [kCFStreamSocketSecurityLevelNegotiatedSSL] -- host:mail.spamarrest.com -- port:993 -- socket:0x1917bbc0 -- thread:0x191581a0
4.35 APPEND INBOX.Drafts (\Seen \Draft $NotJunk NotJunk) "24-May-2009 17:21:45 -0700" {5050}
READ May 24 23:00:29.356 [kCFStreamSocketSecurityLevelNegotiatedSSL] -- host:mail.spamarrest.com -- port:993 -- socket:0x1917bbc0 -- thread:0x191581a0
+ OK
WROTE May 24 23:00:29.367 [kCFStreamSocketSecurityLevelNegotiatedSSL] -- host:mail.spamarrest.com -- port:993 -- socket:0x1917bbc0 -- thread:0x191581a0
X-Uniform-Type-Identifier: com.apple.mail-draft
From: Chip Roberson <[email protected]>
The next thing I see is a timeout on thread, 0x191581a0:
READ May 24 23:01:29.355 [kCFStreamSocketSecurityLevelNegotiatedSSL] -- host:mail.spamarrest.com -- port:993 -- socket:0x1917bbc0 -- thread:0x191581a0
* BYE Disconnected for inactivity
It would seem that my client is in a wait state, waiting for a response from the WRITE which it does not get a response. Given that I have written to this Drafts folder before, I know it can be done but right now I can't.
SpamArrest swears they don't see anything on their side and that the problem must be on my Mac but what could it be?
The only other clue is that immediately after the Disconnect message, I get the hashtable error:
READ May 24 23:01:29.437 [kCFStreamSocketSecurityLevelNegotiatedSSL] -- host:mail.spamarrest.com -- port:993 -- socket:0x1917bbc0 -- thread:0x187564f0
BYE [ALERT] Fatal error: INTERNAL ERROR: Keyword hashtable memory corruption: Input/Output error
That seems to be a direct result of the timeout but it's hard to know for sure. I wish I knew what "keyword hashtable".
I've done all the standard stuff (e.g. rebuilding, reindexing, permissions, etc.) so I'm struggling to find something else to do. I just wish I could get some more visibility into the problem. Given the symptoms I'm seeing in other threads in this forum, I don't think I'm on the only one with this problem. Am I?