Mail.app DoS

["David N. Blank-Edelman" <dnb@ccs.neu.edu>]

Hi-
  Given the preponderance of macs in edu, I'm curious if other sites have seen this particular phenomena. I'm about to burn a support ticket on this because it is getting a bit troublesome.

We're seeing an unpleasant situation where by if a Mail.app user deletes a bunch of messages and then empties their trash folder, sometimes Mail.app gets into this tight loop with out Zimbra 5.x server. Mail.app at that point starts to send commands at a rate of N per second when N is a surprisingly large number. Zimbra, in turn, logs tens of thousands of lines that look like this:

> 2010-05-04 11:41:35,306 INFO [ImapSSLServer-634329] [name=user@zimbra;mid=419;ip=ip;] imap - S: 291726.299 BAD parse error: invalid message sequence number: 1:*
> 2010-05-04 11:41:35,362 INFO [ImapSSLServer-634329] [name=user@zimbra;mid=419;ip=ip;] imap - S: 291727.299 BAD parse error: invalid message sequence number: 1:*
> 2010-05-04 11:41:35,432 INFO [ImapSSLServer-634329] [name=user@zimbra;mid=419;ip=ip;] imap - S: 291729.299 BAD parse error: invalid message sequence number: 2:*

while this is going on. As you'd expect, this drives the load up on the server significantly and only abates when the bad connection goes away. I haven't yet stuck a sniffer on the line to catch the precise command it is sending. If mail.app is restarted or the connection forcefully broken, the mail client becomes sane again.

I haven't found much in the forums (we added a message to this active thread http://www.zimbra.com/forums/administrators/32576-mailbox-log-full-invalid-message-sequence-number-errors.html#post182064).

So, anyone else having this fun, and were you able to do anything about it?

       -- dNb